I CONCUR WITH THIS GENTLEMAN ON LIVE STAGE. 9 TIME OUT OF TEN YOU'LL PROBALY RUN THRU A DI AND COME THRU THE MONITOR MIX.WHAT I LIKE TO DO I A SITUTION LIKE THAT, IS GET A NICE CRISP MONITOR SOUND AND LISTEN TO THE RIG BEHIND YOU AND THE MONITOR SOUND IN FRONT.THEN STAND IN THE MIDDLE OF THE TWO AND IT'S LIKE HAVEING STERE0 TONE.( MAKE SURE THAT THE PHASE OF THE TO SET UPS ARE BALANCED.It all depends on what you're using the amp for.
With good FOH support (meaning the amp is essentially just your stage monitor and the audience is hearing your DI or mic'ed signal through the PA) a 1x15 with a few hundred watts should be fine for a club sized venue.
The carry the entire room, especially with that kind of band, you need much more displacement as well as more power.