I bought a nearly new Cube 100 after borrowing a friend's cube 30 for a while. The 30 had enough volume to cope with a 10-piece show band in a large theatre, but was lacking output for my electric upright on jazz gigs.
My Cube 100 is ideal for all jazz gigs. It coped the other week with a noisy big band (2 vocals, 2 keys, drums, sax, trumpet & trombone) very well with no distortion problems at all. If you're doing the noisy rock band thing, it'll struggle though. Remember that due to the frequencies, you usually need at least double the wattage of the guitarist.
I use my cube for all theatre jobs, big band jobs, etc. But when things get loud, the full 500w MarkBass system has to come out to play Thinking about it, if you just want something for onstage monitoring, perhaps an Ashdown EB180 with the 15" driver would be more up to the job, or the Ashdown MAG 300 2x10?
I heartily recommend the cube 100, though. It's an excellent amp!