I know a 50watt tube amp might seem too much, but the only reason I suggest the ENGL Screamer is because although it's 50watts...it can just just as low volume as any modeller and still sound awesome! There is something about the ENGL design and probably a lot of the gain comes from their complicated pre-amp stages but even on my ENGL Savage 120 (a 120 watt tube head through a matching 412) it can go down to crazy low volumes and still sound great. I actually play this thing after dark some nights when my family has gone to sleep and my sister is just in the next room! I'm telling you, the ENGL Screamer will do it at any volume, you should go try one out just to see what I mean.
I guess they just have very effective master volume knobs that can go very low.