Well.... once again, my GAS has changed (seems to change on a daily basis). Last week it was for a Gallien-Krueger setup, but the current flavor of the week is Mesa/Boogie. I'm looking into buying either an M-Pulse 600 (600 watts into 4 ohms), or a Big Block 750 (approximately 500 watts into 4 ohms). I'd be using one of these units to drive an SWR Workingman's 8x10 (4 ohm impedance and 800 watt power handling). It would see all of its use in a modern hard rock band (about the intensity of Nickelback, occasionally a bit harder, but with a Joe Satriani-esque guitar virtuoso), so a bit of grit and grind is typically a good thing. Would these be good heads to drive that cab (from the standpoint of power and headroom)? Would I be able to get any overdrive out of the M-Pulse 600 despite its lack of an overdrive control? If the power handling of the Big Block 750 proved to be insufficient, would it be possible to add an extra power amp? Which would you generally prefer.