the professional tube one, not the 65 reissue.

would I be forever, forever ever ever happy with it?

Not that it'd be the last amp I bought, but hypothetically if it was..

Tons of clean headroom,
it has it's own gain, but either with it's own gain or an overdrive pedal would I get a nice overdriven/distortion sound (but i'm not talking heavy metal or anything, just classic rock)?

Umm that's all the factors I could think of..

can you output it to a cabinet later if you wanted?

Would it sound better than basically any other Fender amp that costs less? as far as clean, sweet tones go
Yes, yes, yes, yes. Except I do like the Deluxe Reverb more than the twin, but If you need a 212 this is the best option. You can wire it to another cabinet, easily, with just a cable and can play through both the cab and the combo speakers I believe. Any fender Alltube amp is gunna sound nice no matter what.
Yeah Dimebag is not the "Greatest Guitarist" of all time... Hendrix maybe... I must go get food to eat with my mouth

$250 for an amp? wow. is it worth it to invest that much in the amp?

ah that's what I was afraid of.. I was thinking "a lot of people love the sweet tone of the DRRI.. but the Twin has to be better right?" but as with everything they're just different eh?

is the difference huge?

heh so basically this amp would basically pwn any solid state amp?
The best thing to do would be to go and compare it to a DRRI, and see which one you prefer...
"Breathe, breathe in the air
Don't be afraid to care"

Fender Strat/Tokai LS80>few pedals>Orange Rocker 30
If its the amp that offers you the holy grail of tone you want, then yes, you'll be happy forever.
Black Jackson Dinky 2
Peavey Envoy 110
and that's it.