But, you could easily get away with a 65watt solid state amp.
I played many gigs on a Marshall Avt50(when my Laney was in the shop for repairs). The Marshall was not as loud as my 50watt tube Laney, but that is not a bad thing, as with my Laney I never really turned up past three or four.
If I were you I would look hard at the Line6 SpiderII 1x12 or even 2x12, either that, or look into a Peavey Classic30 of Classic50.
You will obviously need to determine the amount which you are willing and able to spend, then see what you are able to get with that...
If this is the first big amp you are buying, a stack is overkill...they are a mission to carry around and generally not needed...but they are awesome to have and they just look so stylish, dont they?
I would go with a small(30watt-50watt) tube combo amp if I were you...but shop around!
[FONT=Century Gothic]Hope is when we feel the pain that makes us try again[/FONT]