Many, many amps work well. I ran Atma-Sphere MA2, Viva SET's, Wolcott 220, VTL 750's, McCormack DNA 1 mono, ARIA Audio WT hybrid, Llano 300 watt mono blocks, Counterpoint SA4's, and AirTight ATM3.
Truth is, they may not be the last work in efficiency but are a reasonably easy load, except for early models that have big impedance in the deep bass.
Lots of people like the Parasound Mono bocks too, although I have not heard them in my home. If I had to rate in order, the best sound (of the amps I've tried) first place would belong to the VTL 750, then a toss up between Wolcott and Atma-Sphere with the Viva coming in there strong for midrange magic, although Viva's are inadequate for anything more than low level listening as they only produce 24 watts.