The most extensive "trial" of amps for Quads (originals and Wayne Picquet modded )I have heard of was done a couple years ago by Robin Wyatt, of Robyatt Audio, and a couple of his friends - Gary Krakow, the tech columnist for MSNBC and David Chesky of Chesky Records. They tried about two dozen amps including many of the usual suspects - Music Reference, Berning, Quad, ARC, VTL, Bedini, etc.. The favorite amp was the very expensive ASR Emitter I Exclusiv Blue, but the second favorite amp was a relatively inexpensive modified Rogue Atlas (bigger power supply, upgraded parts) using EH KT90 output tubes. The speaker cables used probably cost more than the Rogue amp! You can find the complete list of amps tried in an article at 6Moons: http://www.6moons.com/audioreviews/roadtour7/roadtour3again.html
