Better 2-channel music

"06-10-15: Pkelly1504
I would recommend a 2 channel preamp with home theater bypass."

I agree. If you don't have a good preamp, get that first.

Thank you Loomisjohnson, Pkelly1504, Akg_ca, and Zd542. I've got the idea now. Will the Emotiva XSP-1 be a good choice?

I find that the weak point with Emotiva is their remote controls. Keep that one in mind. I'm using the UMC200 with an Oppo 105. I let the Oppo do all of the processing. The only thing the Emotiva does is 7.1 volume control and occasionally radio or other analogue stuff. The sound is great. The one really strong point with the 105 over the 103 is audio. Better processors and dedicated 2 channel out.
You could keep the marantz as your controller. It has a better remote than the emotiva. Upgrading to a 105 should solve the rest of your issues. They do should have a 30 day return policy if the 105 doesn't work out for you.

Like you, I went from a Pioneer Elite AVR powered by separate amps and had OK 2-channel sound. When I replaced my Pioneer Elite AVR with a Marantz AV7702 home theater preamp, I was shocked at the difference. The sound was much more life-like with a better overall balance from the highs and lows. One thing I always felt I missed with my Pioneer Elite AVR was mid to low bass with my Magnepan IIIa speakers. Once the Marantz AV7702 was put into the chain, it was like my Magnepans were a completely different speaker. More mid and low bass with clearer mids and highs.