I have a 20 on my main system for my sources and pre. I currently have my Pass amps also connected but I found little to no difference from direct to wall. Second system I have a smaller (12) also for sources and tube pre, not hte amp (Levinson 23.5) as again I found it signifient with sources, not so much with amp.
Got them both during X-Mass deals, but they currently have recon sale going on. My firt 20 have a defective board for the remote. Tech was very helpful in trying to trouble shoot it before I had to return. They shipped replacement prior to mine going back.
First class service as far as I am concerned,