In the past, I owned the (2) M-500,(2) M-400 and my brother owned the Sonic Holography Preamp.
Today, I still have one of the M-400 (it needed new caps) but it still sounds great and is used in my rec room daily.
As I stated previously in this thread, I now own the 350 tube amps. And yes, Bob Carver himself visited my home last year when there were issues with his speakers.
I view Bob as a creative genius that truly thinks outside the box.
ozzy