I have settled on the amplifier head to buy for my guitar, but I am not sure of the cabinet yet.
I know that there are open-back vs closed-back options, and I assume that the quality of the speaker cone matters. And there is obviously a choice of size and price (for my purposes, a 1x12 will suffice).
What factors are there to consider when buying an amplifier cabinet? How do these affect the sound? Additionally, brand comparisons (or links to comparisons) are appreciated.
Here are some generalizations about the basic factors influencing speaker cabinets:
Finally, you must make sure your cabinet's impedance matches the impedance your amp is expecting. If the cabinet has too much impedance, your setup will inefficient, and you won't get as much volume out of your amp. Too little, and you risk your amp overheating and melting (very bad). If you use two cabinets with the same impedance, their combined impedance actually cuts in half, not doubles (to all you EE's out there: yes, not if they're combined in series, but 99.99% of multiple-cabinet setups are combined in parallel). This is why most 4x12" cabinets are rated at 16 ohms while most big amp heads have a 8/16 ohm switch: If you're using just one cabinet, you set the head to 16 ohms, but if you're using two, you set the amp to 8 ohms.
I won't offer any brand recommendations because I don't know what sound you're going for. But these guidelines ought to get you started, at least.
Alex already covered most of it, but I still have something to add here, which is more like an advice.
You should try the matched box for you amplifier first, to get some impressions. (Most brands have all three common sizes (4x12,2x12 ans 1x12) for their amplifiers available) This way you can either be satisfied (in this case, go get the box) or you can tell what's not right with the sound and you can narrow your search.
You said that a 1x12 is sufficient but I'd recommend you check some 2x12, too. They usually unify the best of both worlds. They generally have a much wider and more open sound than a 1x12 and you have to option to use them in stereo AND they are generally cheaper and lighter than 4x12 cabinets. (ergo: easier to transport!) There are also upright slanted models on the market, which have the benefit that you can hear yourself better in band-context, since like a 4x12 the upper speaker(s) goes in the direction of your ears when you stand in front of it.
Btw. You haven't mentioned for what purpose you need that amplifier, because IT DOES make a difference. My advice is targetet to you in the belief that you'll use it in a band context of some sort. It may be a bit overkill to use (for example) a slanted 2x12 with V30 loaded in your bedroom. When I think about it... It's cool anyway! But there's the budget... and the neighbors!
Take Alex' advice about the impendance very seriously! But other than being more or less efficient, 8ohm and 16ohm setups will sound different, too. 16ohm tend to sound more "vintage" (muddier) and 8ohm more "modern" (tighter), but it's a small difference. (but still, a difference)
In general I'm against brand recommendations, but if you want: I can recommend, since you seem to have a rather tight budget, the house-brand "Harley Benton" of the shop "Thomann" (http://thomann.de/). Yeah, you heard right, a house-brand. But somehow they managed to put cabinets on the market with an insane price-performance-ratio, like a sturdy 2x12 with Celestion Vintage 30 loaded for ~200€. The only down-side: They ship to europe only. (I can't tell where are you from) But you can also try to buy a used cabinet on ebay.
Well, that's as far as my recommendations go. I hope you can use some of it.
A small addition sort of covered by Markus and Alex, but one that is quite important to me:
I far prefer the sound of a 4x10 cab to a 2x12 - it does take more space and is annoying to lug around, but you get decent volume and you can mic up one of the cones for a tight sound for house PA or studio recording.
(not sure whether this should have just been a comment, tbh - mods feel free to move it if you think it doesn't warrant answer status)
I cannot recommend any speaker cabinet without knowing what's going into it. Matching cabinets, speakers, and heads is a delicate and annoyingly unpredictable game. For example, my VHT/Fryette 50 cl through my CAA 2x12 with v30s is not very loud, but sounds good, compared to my Brown Note dumble-style amp, which is only 30 watts, yet is very loud through the CAA, and sounds painful. Also, small differences between specific cabinets, like the bevel, the speaker-mounts, and the shape/dimensions, wood type/quality, and construction technique can have major effects on the sound and how it responds to different amps. You should be very specific when asking about cabinets, describing your amp, your needs, your limitations (heavy lifting, price), and also your sound preferences. Lots of people have different taste.
Other factors I have found while researching speakers:
Factors that I am less clear on are the speaker's wattage and sensitivity. As I understand it, the both of these greatly affect the output volume.
Brands I have found:
