The Naim is similar to Krell in the way it presents detail. All detail no matter how subtle it was meant to be is plainly heard. This gives an impression of lack of depth. It also makes it more difficult to fool your brain that the performance is in your room or you are at the venue. This could be consider a down side. But the up side is you do hear all the detail easily and these types of amps have incredible control, transcients and dynamics. The Naim also sounds like it has a very flat frequency response. Although this is instilled in us as a desirable thing, and it can be to some, but flat can also not be as "musical" to some perceptions. You'll have to decide which way you want to go. If you want to lean more toward the Marantz sound but with more detail I'd suggest listening to some more tube gear. I personally would suggest Conrad Johnson if any is available to you. It sounds like the Marantz was more toward what Conrad Johnson does on some of their gear, the vocals are more pronounced/emphasized and bit forward from the accompanying instruments. Whether this is intentional or just a side effect of a very lush midrange I can't say. Elapsed has a Naim system and he found his nirvana by going all Naim. He says the Naim units have a synergy with each other. I can believe that because I found the same with Krell.

One suggestion I have is to experiment some with the tube buffer out of the system to see what happens. I'm sure the buffer adds some warmth but take it out of the loop to see if anything changes to the positive. I'm not familiar with you CD player but you might try a Naim player to hear what happens. I'd also strongly consider what Feanor had to say.