Hey, thanks for the replies!

Unwillingly, I've started a discussion.
Er, I guess that was me, pointing out how vague the parameters were.
if anybody wants to share their experiences with 6" or 8" driver combos or maybe a single 10" feel free to reply here. Thanks again for the link.
Well that narrows it down a bit. But what type of music? Drums or no drums? For monitoring your own sound behind a PA, or stand alone?
My own experience: I played a little "supposedly cocktail" gig with a guitarist friend, in the entrance hall outside a reception room of a hotel. It was trio with a light jazz drummer on a little Gretsch kit.
I brought a little 10" combo (one you can't buy in N. America, a DB510 made by a little Danish company called CAD -- used by some Euro double bass players.) Perfectly adequate for the job, I thought.
We started playing background music (Girl From Ipanema, etc.) until some of the crowd started listening to us and watching our excellent guitarist intently. This encouraged him, and he started calling more upbeat and louder stuff. The crowd was responding, and clapping.
Well, long story short: before long, people were shouting Smoke On The Water! We didn't play that, but we actually ended up doing a couple of Cream tunes. :^D
Our volume quadrupled over the hour. (We only got away with it because the lady who hired us is a friend, and a musician herself -- she was glad the crowd loved us).
Volume cranked, my little combo could be heard, but I couldn't get enough low end to really keep up with where the music went, even cranked.
Worse: I think I may have permanently damaged the speaker; it's sounds fuzzy at higher volumes now. :^( I should have resigned myself to having a midrangey sound, and left the Lows flat.
Anyway, the lesson I took from that was: Always bring more amp than you expect to need.