Seriously I have never played with anyone with a 100w guitar amp before and I never want to. The most power I've played alongside is a 50w Mesa 5:50 going into a Dual Rec 2x12 and a 50w Vox AC50 going into a Marshall 2x12... Those things get loud enough / too loud and the masters arent even above 9 o'clock. Another guy I just played with used a Epi Valve Junior, 5w into a 1x12 Fender Deluxe cab... volume around 8-9 o'clock and it was just perfect. This is in a setting with live drums, live bass amp, monitors pushed, gat amp mic'd, Keyboard, 2 acoustics, 2 vox and a choir and that little epi was loud enough
I once was at my mates place and let the Mesa go full bore, took the cab outside, aimed it away from the house and it was still shaking the walls and left my ears ringing for a couple hours after that... and I was inside...