Get a tube amp.....but I'm a tube amp guy, so take it for what it's worth.
Solid state may have more variety of sounds, but will never sound like a tube amp. A 50 watt tube amp will always be a lot louder than a 50 watt solid state amp. Maybe you would prefer to have a tube amp with a bunch of pedals in front of it? If so, then the spectrum of available pedals is a whole nother outer limits of debate and tastes....
Keep in mind that, as a very general rule, tube amps with more than one speaker are designed to be loud, but are not usually stereo. Solid state amps that have more than one speaker will usually have stereo fx or stereo models. If the amp does some stereo fx, then you will have to decide if you want to be able to record it in stereo. More to do, more gear, more to learn for stereo.
How powerful or how loud the amp is has nothing - or very little - to do with how it will sound when you play back the recording. Some very large, awesome tunes were made by recording some very small amps. Use the wattage and loudness factor in your decision if you are also planning to play live at gigs or some where other than recording in a studio setting. If it will always be studio recording and nothing else, then 30 watts - 50 is pushing it, but ok with me - is plenty for any recording you will ever do.
In my obviously humble opinion, nothing will effect the sound of the amp as much as changing the speaker. You will pay more for an amp that comes from the factory with a good speaker already in it. Amps are like car stereos.....the manufacturers expect us to put better speakers in them. You wont have to hunt very hard, cuz if the amp comes with a killer speaker, the advetrtising will say so, it will probably be a selling point. 12 inch does sound different than 10 inch, but I myself prefer the 10 inch sound. I dont like speaker breakup (like most guitarists seem to) so I put overqualified speakers in my amps.....for example, I use a 100 watt Weber Michigan with my YCV20WR, and it screams tube distortion without screamin speaker breakup, and I love it that way. However, I have a 1x12 Weber Michigan cab and a 2x10 Eminence Legend cab, and it is very difficult to tell them apart, the difference is there but it is very small. The Greenback that came in the YCV20WR is really a great speaker, but I like my Michigan a lot better. Sum it up by saying this: Dont just play an amp "as is" on the show room floor and judge it good or bad without first plugging it into a few external speaker cabs to see how the sound changes. Many amps that sound like crap "as is" will really smoke and scream when plugged into a topshelf speaker cab. The little
Epiphone Valve Junior 5 watt combo is quickly becoming a good example of this. To put it politely, the thing totally sux "as is" but plug it into a great cab and it just simply comes live......again, in my obviously humble opinion!
If you really are going to use it for recording and nothing else, then you can get a really nice small wattage tube amp for the same money as you can get a very hi wattage middle of the road solid state amp.
Just some things that come to mind off the top of my head:
Traynor YCV20WR or YCV50 Blue or YCV80 for louder than loud.
Vox AD30VT or AD50VT. Hybrid with a lot of variety, and a cool "power soak" knob on back so you can lower the speaker volume without changing the tone. Needs a better speaker though to realize it's true potential.
Peavey Classic 30......my next purchase. I am trying to sell my Vox so I can get this one.
Traynor TRM40 for the budget minded who wants variety, two 20 watt channels, with two external speaker jacks, and a beautiful chorus sound, $160 delivered. Sounds absolutely huge plugged into a 4x10 cab.
Mesa gets the most recommends, for a good reason......it's good.
Rivera for those with money to burn on amps that sound even better after falling off a truck and rolling down a mountain......this is what I would buy if I won the lottery.
I wont even pretend that I know anything about the so-called "boutique" stuff. And you have to do a LOT of homework before you buy, because the list of amps that you should avoid like the plague is a lot longer than the list of good amps.
After you have conquered this challenge, the next task will be getting your playback sound to sound as close as possible to your amp sound! You might want to get an advance jump on this by reading up on mic choices and mic placement.