I have a 1x12 Marshall JCM 2000 combo and it sounds great.
My only criticism is with open back amps you seem to loose some bass projection, i suppose thats why all the Metal bands go for closed back cabs. Incidently, my amp is 40w (valve) and it can drown any drummer out and is suitable for most venues.
It does crunch up a bit on the clean settings though but that is because i'm really pushing the volume.