If you jam with anyone else, I just want to point out that unless it is a mellow jazz combo, drummers are loud. It's easy to get buried very quick. Also, if you have an open back combo, the louder you get, the more the bottom end wants to drop off.

If I needed to do that again (and I have no desire to at the moment...), I would be sure to at least get a 2x12 closed cabinet and ensure that my amp had an out for it. I've mentioned in threads gone by about my arcane 80's rig which was a 70's era Peavey Classic 212 combo (SS/Tube hybrid), generic 4x12 cab and a Cry Baby running through a Boss Turbo Overdrive to the front of the amp. Easily the dumbest sounding set up but it was huge tone. Before I added the 4x12, bedroom jamming had great tone but when I jammed with other musicians or when I started in a band, the bottom end just died. So, I tried a friends 4x12 with my rig (if you want to call it that) and it sounded really good so I bought a cab.

Anyway, a good, lowish watt amp will do but be mindful of how it will sound when it is at a volume that when you need to hear it over other players, it will not sound like a dying cat.