on an intuitive level, I'd agree with the guy from Svetlana. My guess is there are some micro-variations in the a.c. signals that are lost when a neg. feedback loop "blends" slightly different parts of the signal together, and this causes some loss of the cues that give our brains the sense of "live" music. It's almost standard when someone hears my system the first time they say "It sounds just like live music" whatever the recording...but even more so on older, more simply recorded music. The better p-p designs I've heard use no or very little neg. feedback, good tubes (like el84's), and quality iron. Many folks need the higher power because they have to drive less efficient speakers for "decorative" reasons...I'm glad we don't have that problem!!