If you need some power and want SET then NAT or KR Audio are really the only two that I have heard that deliver the SET magic with real bass power and control. The biggest Ayon monos are not bad either but despite plenty of power sound kind of soft in the bass. For somewhat easier speakers they are one of the best but for "normal" or electrostats stick with NAT or KR.
I drove my Acoustats (1+1, Spectra 2200 and Spectra 4400) very nicely indeed with my KR Audio VA350i. It also is driving my Genesis III speakers with real authority, even though they are 87db and 4 ohms. No problems. I have hooked it up to a number of Apogees with great success as well (not the 1 ohm Scintilla mind you). The bigger KRs have more headroom of course. The NAT amps have similar punch and drive and perhaps sound a bit more tube like (KR Audio amps are hybrids) overall.
