I think for factory stuff, its hard to beat a Fender Blues Junior. You might want to add a distortion or overdrive stompbox, but the amp on its own should cover what you're looking for. And there really isn't much difference in the loudness of a 15 Watt and a 50 Watt amp.

I hear, and read, good things about Pignose, but I haven't actually played one, so that's just hearsay.