While AVA Frank replied to me over the summer indicating the SET 120 and SET 400 effectively have the same circuit design and the same Exicon MOSFETs (and "sound the same"), (with fewer of the same MOSFETS on the 120) I'd like to see an internal photo shot of the 400 to compare torroidal transformer sizes and quantity of caps. The SET 400 is 8lbs heavier by shipping weight, and we know the added mosfets don't weigh that much. Yes, the chassis and larger footprint on the 400, more metal top half of chassis, maybe larger heat sinks..., but wonder if there are different size or quantify of transformers in each of these size amps.
My dilemma deciding between the two with 87db sensitivity speakers would be LOW listening levels, not just "watts". Would the SET 400 have more drive compared to the SET 120 at lower listening levels. ??? Went through this same scenario with several former B&K MOSFET amps, 50w, 100w, 150w, 220w with the same mosfets and circuits and the yet 220w Dual Mono amp with dual torroidal transformers was significantly better, with much better drive at low volume listening levels with my own 87db Totem Acoustic Signature speakers at the time. And, 38lbs for the SET 400 seems kinda light weight comparatively to my former 200+ class A/AB amps all closer to 79 to 87lbs. Maybe "Less is more" in the circuit so to speak, would have to demo both to hear it first hand. In my case, even with 92db speakers I'd probably end up with the SET 400, but I'd have to demo both back to back to be sure either way.
hilde45,
I'd also check with Jim Salk and ask him too. He'd know for sure which would be better with your particular Salk monitors. Fun project. Good Luck.