preamp for Revel M22

I run AES DJH preamp and Sixpacs, both with Jensen paper-in-oil capacitors, and am immensely satisfied with the sonics. The little DJH preamp is tube rectified and direct coupled, which I believe makes all the difference in the world!

I have also had good results with SimAudio electronics and my M22's.

You've probably realized that the Revels are highly placement sensitive. But once you get them dialed in with the right equipment, they are spectacular speakers. Have you considered an integrated amp? That would be only one piece of gear to swap and less cables...whatever you decide should be a significant improvement over your Onkyo receiver