I have heard the 3.7s on many occasions with many amps. (including my own) I have said this a bunch, but there is something special going on with the Krell amps and Thiel speakers. The best I have heard the 3.7s (in order of preference) is with the Evo 600 monoblocks, Evo 400, FPB 650M monoblocks, Mcintosh 1201 monoblocks, Ayre M-xr monos, All were very nice systems. But the krell/Thiels went from very good to having the WOW factor going on.