The brightness worries me. My amp (mesa F50) is already one of mesa's brighter amps. But Mesa cabs are about twice the price of the avatar ones. I have heard sound samples of the mesa f50 with an avatar 4x12 cab with v30s and it sounded good so maybe i'll still go that route. How much of a difference tone wise would a 4x12 cab make rather than a 2x12 or 1x12? I'm talking about for recording only.
Well, Vintage 30s are dark enough that I don't think it would be an issue. I manage to get darker tones from my Mesa Stiletto Deuce into a Marshall 4x12 with V30s, and the Stiletto is certainly capable of being very bright.
Vintage 30s are dark speakers to begin with- they don't have a ton of treble and they have a tight, focused low end. There are people who consider the V30 bright or harsh, as it has a pretty noticeable spike in the upper mids, but as far as I'm concerned, bright = treble, and something like a G12T-75, with its scooped midrange and emphasized top end is bright, while a V30 is inherently dark. An Avatar or Marshall V30-loaded cab is only bright compared to something like Mesa or Orange, the latter especially, which are thick, heavy cabs with a ton of low end.
I've had good success taming bright amps with my V30 Marshall cab. Along with the Stiletto, I've used it with a Marshall JCM 2000 TSL and a 1976 Marshall JMP 2204, the treble on which could reach icepick-to-the-ears levels really quick, and it performed admirably. Where She Wept on the forum here has heard my tone with both those Marshalls through that cab, and I think he'd attest it wasn't harsh at all. It's also matched up with the darker amps I've used it with- Mesa Mark IV and Bogner Shiva, among others- pretty nicely.
Comparatively, a 2x12, even an oversized one like the Avatar Vintage will give you tighter lows than a 4x12. Overall, the 2x12 will sound more "focused" while the 4x12 will sound "bigger". 1x12s can have a nasty habit of sounding boxy, as they'll lack quite a bit of lows compared to a 4x12 or a good 2x12. The oversized Avatar 1x12 shouldn't have an issue in this department, though, and if you want to go the Mesa route, a Mesa Thiele 1x12 is one of the best 1x12s on the market for rock and metal tones.
For recording, if you're close-micing the cab, you should be able to get away with a 2x12 or 1x12 without an issue. If anything, it might be an advantage if you need clarity in lower tunings. There will be a difference, but it's not going to be one that'll make your tone unusable. It won't sound quite as large, as you're not moving the same amount of air and getting leakage from the other speakers into the mic, but it may be more controllable in the mix.
Hope this helps.