Rockport uses Gryphon Class-A amps (I'm sure among others) when voicing their speakers, but they may be out of your price range. However, considering that along with the sound characteristics you're looking for another Class-A amp might be just the ticket. I think something from Clayton Audio would be a great match, or maybe a used Plinius SA-103 or Pass Labs amp. Just make sure whatever amp you get has enough power to allow the Miras to open up to their fullest. You might ask Rockport for recommendations as well. Best of luck.