The trick to keeping up with un-disciplined guitarists is a little more power and a lot more speakers. 2-15's OR at least 2 maybe 4 12's OR 6 or 8 10's (or a pair of 410's) AND a few hundred watts to drive them. That's not really combo amp territory except for maybe the largest, most powerful one that also has ability to add cabs to it, not sure, I haven't bought a combo in a long time.
You can get it in the used market though and stay within your price range or at least the top end of it.
It would be a lot cheaper, easier and be much less crap to haul around if your guitar players would turn down a bit, ya know. Like think of your overall product/performance and not just themselves....good luck with that one.
