Re: 15 watt amps
I have a couple 15W amps. The Blues Jr. never gets turned up above 3.5 on the master without getting the hairy eyeball from the rest of the band, and it sounds like crap through an attenuator. Still, it's my go-to amp because it has nice cleans and nice growl.
It seems like even a 5W tube amp is too loud for bedroom/apartment use. For a club you should be mic-ing your amp anyway, otherwise your sound guy won't have the levers to get a good balance in the room. In that case, 15W should be plenty and 100W is probably a bit too much.