I have an Ibanez JEM Jr, the cheap version of Steve VAI's signature JEM model (costs around 500$ compared to the 1600$~2700$ regular JEMs run for). There are many differences, among them that it uses Quantum pickups instead of DiMarzios. It plays well, but it doesn't sound that good.
Is it worth it to upgrade the pickups to DiMarzios similar to the one on the high end JEMs? Would it really improve the tone of the guitar and make it close to that of a high end JEM?
Better pickups, if properly matched and installed correctly, can make your guitar sound better. Many players upgrade their pickups to improve the sound of their stock guitar. Certainly putting in the same or similar pups as the higher end model should help your sound considerably, as long as they are electrically and mechanically compatible. (Not a certainty.)
Will it sound as good as the high end model? Probably not, because other factors besides the pickups go into making a guitar's sound. The internal electrical components may be of better quality on the high ender and numerous other things might be different: Quality of the wood, method of construction, nut material, bridge construction - any number of aspects that can impact your sound. (Things like 'tone woods' in the body, fingerboard woods, and nut material are sources of endless debate among musicians playing electric instruments: Some believe they make no difference in an electric, others will pay considerably more for a guitar body or neck made of a particular type of wood...)
That being said, along with the strings and your own technique, the pickups are the most important link in your sound chain (we'll leave out the amp and speakers which are completely external) so if you get the same pickups as the high ender (or any better pickups that are suitable for you and your guitar) and make sure that they are installed properly (very important) you should hear a significant improvement in your sound.
More than that, sometimes there really is very little difference between a high end model and a lower model outside of the pickups, for example. You often pay more just for cosmetic differences - a nicer paint job, pearl inlays instead of plastic, a natural bone nut instead of synthetic bone (etc etc etc).
Also having "the bona-fide signature model" or a "Made in Japan" or "Made in America" model instead of "Made in Indonesia" model will jack up the price, although objectively speaking the "Made in Indonesia" or "Junior Model" might be just as good.
All such factors generally have little or no effect on the sound and playability of the instrument itself (outside of the player's mind - people like to think that if they paid more, it sounds better...).
Unfortunately, it's not always easy to find out the truth about the differences: The makers, the dealers and those who buy the expensive models all have an interest in keep those matters secret. Ibanez and their vendors certainly don't want people to know that they're paying double for the "high end model" because they're getting pickups worth another $100, mother of pearl inlays instead of plastic, and the labor is more expensive someplace, while the instrument itself is virtually the same!
I know bass players who will buy a Fender Squire bass for $300, change the pickups and the wiring or pre-amp and claim that it sounds as good as the $1500 American made model.
Bottom Line:
Try to do some research about others who have done what you want to do. It's probably a very good idea - well worth it. But unless you are familiar with guitar electronics, etc. you might want to have a guitar tech install the new pups, or at least get some advice from one.
I have often found that the pickups are what lets affordable guitars down the most. It will definitely make a considerable improvement, but it still may not be worth it.
The change of the pickups is not going to make the feel or the look of the guitar any better. It is also not going to make the acoustics of the guitar any better.
A pickup does exactly that it pickups up the sound that the guitar makes and converts it into a signal your amp can amplify. If the acoustics is poor in the instrument then the best pickups in existence are not going to make it sound good.
I would caution you to not try and polish your turd too much, rather upgrade your guitar when you have the means and the skills to justify it.
I think the best answer (hinted at in the other answers so far) is:
There are many factors in how your current guitar sounds. Pickups may be the primary factor, but they would only make up about 50% of it. That is why upgrading the pups won't be a cheap upgrade. That said, if the guitar sounds "bad" because of poor intonation, for example, then new hardware won't help at all.
The main reason I said "it depends" is because your target sound (as made by the signature model) has been amplified and processed through unknown equipment. Unless you have the same amp and pedals and whatnot that Steve Vai has, comparing your sound to his (both before and after new pickups) is a fruitless exercise.
However, if you have a personal tone you are developing, then upgrading pickups would be a step in that process (if you aren't going to upgrade the entire instrument). However, I'd say to find the amp you want first, then work on improving the sound of the guitar.
While pickups upgrades are a way to get a different sound, I would recommend that you try adjusting your pickup height before resorting to a pickup swap. In many cases, poor pickup performance is more about poor pickup height adjustment rather than the pickup itself.
I personally like my pickups to be level and then start with the bridge pickup 1.6mm from the bottom of the wound E string and the neck pickup 2.4mm from the bottom of the wound E string. This measurement is taken while depressing the wound E string at the last fret on the neck. Once the height is set, play the guitar use both clean and distorted sounds. Use your different pickup combinations and adjust the pickup height until you are happy with the tone.
If you have humbucker pickups you can also balance the poles on the pickups. Poles that are either hex or flat head can be adjusted to fine tune the tone of the guitar. Google “balancing guitar pickup poles” for specifics. Again, use you ear and fine tune the sound to your liking.
If you try this exercise and determine that your pickups simply cannot give you what you want, a pickup swap may be in order. Do your research and know what you are looking for in your sound then select a pickup that will deliver the tone you want. I know people who have drawers filled with pickups from failed swap outs.
Another thing to consider is some other weak spots in the tone chain of tremolo equipped guitars.
Sustain blocks are a big contributor to under-performing instruments. Sustain blocks are commonly downgraded by manufacturers to zinc alloy or pot metal from brass to cut production costs on lower price point instruments. Light, soft sustain blocks absorb more vibration from the bridge. Heavier, denser sustain blocks will leave more of the vibration in the string where the pickup can translate the vibration into amplified sound. If your guitar is not equipped with a brass sustain block, upgrading to a brass block is probably the single most impactful tonal upgrade you could make to the instrument. I use tungten for all of my blocks. It is articulate, resonant and very pleasantly aggressive.
The tremolo claw is another weak point. Upgrade to a brass claw. I do this on all my guitars too. It is amazing the difference this upgrade makes. I do not know the science behind it, but it works.
Finally upgrade your tremolo springs to noiseless springs for a clearer more articulate sound that is free of the clunks, creaks and thuds commonly encountered on tremolo systems.
Given that you can get a good brass sustain block for around $40, a good brass claw for about $20 and noiseless springs for around $15. You can spend $75 plus some of your own time and make a far greater impact on the tone of your guitar than a $100+ pickup upgrade would provide.
If you otherwise really really like that guitar, then yes. If there are other things about it that bother you whenever you play, then no. The pickups will improve the guitars sound but it won't be like suddenly having a top end guitar. Having two pickups professionally replaced will cost you almost as much as the guitar did.
i have bought many Ibanez guitars through the years. All models were rg body types. I have replaced every single set of factory pick ups with and EMG model of my choice. 81/85, 57/66 and a James Hetfield singature set. Yes it makes a difference. Pick up companies make pick ups to accomidate the needs and tastes of the player. They have different tones, amount of sustain etc. From metal to rock to blues. I have also used D'Marzio evolution pick ups for and RG model Genesis. If you are noy happy with what you have for the price you paid, then you never will be. If you are looking for more of a Steve Vai sound go with the evolution or Dark Matter pick ups.
