Got a line on a Fisher 400 from the original owner and am considering buying it. I've long admired the aesthetics of these wonderful pieces and have yet to own a tube receiver but have heard a lot of great things about them. A couple of concerns: How challenging is the upkeep on this series? Is it a big task to maintain these receivers? I own a vintage McIntosh MA5100 now and love it but am considering replacing it with the Fisher 400. Have I lost my mind? I replace gear fairly often and am not afraid of trying new options... Is the "warm tube sound" all it's cracked up to be? I would appreciate all opinions and recommendations... thanks.