I'm looking around for used tube amplifiers in the $500 ballpark (combo or head/cab for that much). I will be using it for recording and possibly on stage, so I'd like at least 25 watts or so (more headroom is good).

I would like something with a smooth clean tone like a Fender Twin Reverb with plenty of headroom. However, I would also like the option of a solid drive channel more akin to a Vox AC30.

I would just look for a used Twin, but some sort of gain control or a separate gain channel would be nice.

I mostly play indie, post-rock and alternative Radiohead sort of stuff.
get a used AC15, they run $400 all the time. That leaves you enough for a A/B box so it turns into a 2 channel amp.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
I played through an AC15 a little while ago. It sounded alright, but I don't think it was quite what I wanted. Sounded a bit thin. Perhaps the AC30 would suit me better.