Maybe none of the above Jughead,
If you are looking to improve the 2 channel sound with your VA Mozart Grands, why are you looking at the amp as the problem? Most likely it is the Marantz AVR that is holding you down. The 2 channel pre-amp sections in AVR's are merely an afterthought - AVR's are designed for multi-channel, digital reproduction first. That means movies and games.
You want better stereo, get a component designed to reproduce stereo!
I suggest you look at a good quality 2 channel integrated amp with a HT Bypass feature so you can use it full time in your surround sound system to drive your VA's. I had a ten plus year affair with HT that always left me wanting more from music reproduction. And my front three speakers are almost identical to yours. The amp wasn't the problem - it was using an AVR as a stereo pre-amp that was.
I finally replaced Parasound theater separates for a Marantz PM15S2 LE integrated and it has taken my 2 channel listening and my VA Bach Grands to new heights. Analog sources, vinyl and CD, are plugged directly into this integrated. Digital sources like cable and Blu-ray are plugged into my AVR. The Marantz drives the VA's all the time; the AVR takes care of the center and surrounds.
In your case, you could still use your Adcom amp to drive the center and surrounds. Hope this is food for thought.
