money best spent on better dac, transport, preamp?

The first response to your post is really right on the money. Of course this will not work so well if you still spin vinyl. My suggestion is the Audio Aero Capitole Mark II Cd player that has all of the things you want and it is available used here on Audiogon for a bit more than your budget. I run my DVD player, my Satellite and my multi-disk Yamaha CD player through it.

the latest version even has an analog passthru so you can run your tuner through it; the older versions are upgradable to the analog passthru.

Check out a used Cal Audio Delta transport and Alpha DAC; wonderful units for way less than a grand used.

Trade in the marantz. You have a lot of wasted technology shoved into a box that you want for stereo listening. It's not a bad pre-amp, it's just that it is designed for theater. Sell the Marantz and get something designed for stereo listening. With the big boom in surround sound, you should be able to get a nice deal on a good used stereo piece like classe, audible illusions, CJ....

By the way, to test your d/a, try going digital from the cd to the marantz and listen to the differences?

Cary 303 CDP has vol control on the remote and is my fav for CPD for under $3k. If I had to do it over I'd have the Cary CDP going directly to an amp. If you have a local dealer try to get him to let you demo the Cary 303 (most dealers sell it new for ~2400). You can always buy a better Pre/Proc, but oh what a better CDP can do...