I've narrowed it down to those two. I'll be running a 4 Ohm load (a Mesa Powerhouse 2x15 and a 4x10), and I'd like your opinions on which one you'd buy, given that I want tone versatility above all (I wanna be able to grind out some really gnarly-sounding lines, as well as clean jazz lines and plenty of slap). Volume is obviously important to me as well, but because I've heard that Mesa's amps tend to be as loud as other makers' amps with twice the power ratings, I'm wondering how much of a difference in volume and headroom there'd be between the above mentioned amps (625 Watts for the Mesa @ 4 Ohms, 1000 Watts for the Genz). Genz also mentions that they test their amps with "real reactive speaker loads", and I've heard that Mesa's cabs are reactive loads. Does that mean that Mesa's amps are tested and rated with reactive loads as well? I've played the Mesa for all of maybe half an hour, not enough to get an idea of what it can really do. The Genz I haven't touched yet. Any help would be appreciated!