I use an Art Audio Diavolo, pure magic, and dead quiet.
Apparently, these work well with Avantgardes: (http://tomevansaudiodesign-usa.com/_wsn/page4.html) You might inquire from these guys as to the combo's traits, since they sell both lines; (http://avantgardeaudio.com/index.html) Any high quality SET amp will work well. Keep in mind: Any noise/system shortcomings will be magnified as if by an electron microscope. These speakers are unmerciful in their adherence to the truth.
The Lamm is for sure, but in real world don't break the bank money... take a look at the SAP stuff as did Steve Rochlin of Enjoy the Music when reviewing said item.
I own one of these and its' KT66's are pure magic w/ the 2.2 speakers
I'm using an Art Audio Carissa with my Duos and its very good. As a note of interest I also use Van Den Hul Revelation speaker cables which are the best I've tried with these speakers. Very smooth and airy on top. A touch shy in the bass but they're new and break in time should solve this shortcoming.