I have heard the 3.6's with the McIntosh 501's...sounded very good, relaxed, smooth, deep natural bass, and airy highs. Didn't sound like it was breaking a sweat even at higher SPL's. I wasn't able to compare the 501's directly to my Parasound JC1's, but I suspect they would hold there own. For myself, I'm quite happy with the JC1's driving the Magnepan 3.6's...an amp you may also want to consider for the 20.1's IMHO.
Good luck!
Good luck!