I had the original GFA-555 from Nelson Pass Designs, in the early 1980's. That amp handled some of the most difficult to droive speakers, I had on loan. It drove my big ALON Model IV's and B&W SPeakers in stereo mode, 200 wpc, with no problem. I cant trash it at all. IT also lasted years, being left on all the time, till I sold it. I find the people trashing it, either didn't own one, or are jealous of it, not having to spend a fortune to get sound that they have spent tons of m oney for, and Adcom equalled or bettered theirs. Ray