Thought I'd drop in a few cents worth...
Heard these wonderful ribbons with the Magtec amp from Roger Sanders, very impressive. The current owner (well known in the land of Aus) previously had Quads driven with the ARC Ref75. Got rid of the Quads... due to obvious reasons, and acquired a pair of 3.7i's. Partnered it first with the Ref75 couldn't quite "grip" them too well as the term stated by bonzo. The bass was muffled and certain other freqs seemed somewhat rolled off. Previous owner actually preferred the Quads!
After a bit of hussle and tussle with a few well known power amps, seemed to have settled with the Magtec, and this one certainly delivers the true potential of these new 3.7i's, very good balanced overall sound. The Magtec is also quite affordable compared to other lofty contenders and another amp worth mentioning driving maggies to their full potential was the Plinius- another marvelous amplifier and superbly built in New Zealand! Go the ALL Blacks!
There is another amplifier worth mentioning, since I have had a direct comparison with it driving the MG20.7- the wonderful Mac MC452- powerful and dynamic with all the virtues of pure musicality, very similar to the CJ Premier 350 (a huge beast) that is no longer in production. The only thing is, the preamps used were either the CJ GAT or the ET5, hence I cannot tell for sure which one was offering the "best performance" but I got the idea of awesome tube pre finesse with SS oomph! And on ribbons this is exceptional.
Cheers, RJ