I own a few practice amps/devices including the amPlug, orange crush and line 6 amplifi.
They are all fine, but it depends on how YOU like to practice. Opinions aside, if you want to hear yourself play and you don't have any space and no budget, then the amPlugs actually sound good. Like you said, they are limited especially if you're looking for the chug needed for metal. If you always use high gain or distortion when playing, then get this. (I use the AC30 because I like that edge of break up sound)
Next level up is the orange crush 12. Really great amp for the bedroom. It has a headphone out and EQ for treble, mid and bass as well gain and overdrive. If you don't need a speaker, there is an amp called the "Micro Terror" that works great with headphones, but can also connect to a speaker cabinet.
If you are on a tighter budget there is an amp called the Blackstar Fly 3 that some say sounds better than the Orange crush 12 and it has bluetooth so you can play along with your phone.
If you're going for really customizable sounds, then the line 6 amplifi is pretty good. It uses an android or ios app to select the sounds and settings. You can save them to the amp so its stored in memory without having to constantly pair your device. It's like a premium bluetooth speaker like Bose, so might be a little out of range, but figured I'd mention it. Line 6 Pod isn't bad either, but is in the same price range.
Finally, if use a laptop or tablet it might be worth looking in to getting an iRig or other USB connection. I see this as the general direction practicing is going. The upside is that you can record your riffs while practicing so you don't forget.
Obviously there are a ton of products, but I figured I'd mention the ones I've used and general features.