Others will chime in with more info, but I just love being the first to reply, esp. when it's something I know what I am talking about... (EDIT: Damn! Got skunked while I was composing...)
You are on the right track to go with power amp tubes. That warm, fuzzy, "brown" distortion everybody loves comes from overdriven power amp tubes- there is simply no way you can get "that" sound any other way. Loved your use of the word "tubular," by the way.
The "size" tube (actually the
type of tube) does make a difference in tone. Most tube amps use 6V6, 6L6, EL34 or EL84 as power tubes. Google each type for 15 times more information, and about 150 times more opinion than you could ever want on each.
Fender Twin Reverbs enjoy such a legendary rep because, in the golden age of rock 'n roll, they were freakin'
everywhere- perhaps the stereotypical
performance amp, with from 85 to 135 watts of output. Frankly, NOT what you want for a music room/home recording studio- but if you really want to rattle windows... my 135-watt version rattled the very FOUNDATION of my house. Scary. There is a version of the TR that has a 100 watt/25 watt switch, but you are still pushing air with 2 12's, and lugging around a huge, heavy amp. If you will NEVER play out (or if your playing out will be smaller halls) you will be much happier with a Fender Princeton Reverb. If you want to step up to a "mere" 20 watts, go with a Fender Deluxe Reverb.
I have owned several vintage tube amps over the years- some of my favorites have included:
Peavey Classic 30- vintage looks, 30 watts, very good tone.
Peavey Delta Blues 210- same basic amp, add tremolo (I am just
fruit for on-board tube tremolo.) Somewhat dumpy looks compared to the C30.
Fender Twin Reverb- 135 watts- STUPID loud. But wonderful tone.
100 watts. Almost as loud. Same wonderful tone.
Fender Pro Reverb- 65 watts. Same tone, more manageable. Under-appreciated, so a good deal.
Peavey Bravo 112- EL84 tubes, like a Marshall. Shouldda kept that one. VERY under-appreciated, and do NOT listen to the nay-sayers. A very good amp and an EXCELLENT value.
Ampeg VT-40 One of the few tube amps I have had that had a different kind of tube than listed above- 7027's, which gives it a unique tone. Worth checking out, esp. if you like to NOT follow the herd. Heavy and LOUD.
Fender Champ. Cool little practice, tube amp. one you should consider.
Fender Deluxe Reverb- my fav. amp, will probably stay that way unless I can score a Princeton Reverb for a very nice price.
I have also had some more modern tube amps:
Fender Champ 25SE- a sleeper, very good tone, esp. for a hybrid- BUT WAIT- it's got power tubes, the pre-amp side is SS.
Fender Super Champ XD- my favorite practice amp. Again, power tubes/SS pre.
Ampeg Reverberocket reissue- just got it, have not had much chance to play it, yet.
Fender Twin Reverb- '65 reissue. Also no chance to play it much, yet.
My top 3 suggestions:
1. Fender Deluxe Reverb
2.
Fender Champ 25SE (really.)
3. Peavey Bravo 112.
and a couple more...
4. Fender Princeton Reverb (might be higher, but I haven't spend more than an afternoon with one, so I am reserving some judgement.)
5. Peavey Classic 30 or
DB210.