Whether anyone hears a difference between amps depends on a lot of things. Don't be embarrassed about enjoying the sound of the 6230; it's a nice amp. It is a later design than the Marantz, from the days when there was a heightened awareness of the negative effects of transient intermodulation distortion, so it might even be better.

I don't think I know enough about balancing various pieces of equipment in a system, and your description of the problem means little to me except that you might be having two separate problems. But. . .1) using both a preamp and an amp with input sensitivity adjustment you have to consider "gain structure"; 2) the tweeter in the 4311 may be a little peaky, which would make matters worse; 3) the 62XX series of amps can evince transformer buzz, which you will hear directly, not through the speakers, sometimes with a sympathetic buzz in the case lid; 4)—last and most likely—the conditioner you moved to another spot may have been solving a ground loop which you are now experiencing.