Carver Black Beauty 305 monoblocks. Six KT 120's per side for about 350 watts into the 4 ohm 20.7's. Only tube amps that I have run across yet that can truly drive the 20's without any strain. These ARE the tube amps for Magnepans! Very, very happy with these amps so far!
System edited: Fell in love with the Magnepan 3.6's which I have used for the last three years. Made the mistake of hearing the new 20.7's at the factory in White Bear Lake; the 20's sounded awesome...Ordered a set in early June.
JPS, appreciate the offer but I want to audition the SuperConductors before I buy (comparing them directly against the Kubala Sosna) and I want to keep the runs as short as possible, only need about six feet.