Transparent Stereo From Surround Preamp/Processor

I'll start by saying that I realize that this could have been posted in the home theater section. However, because my inquiry is truly in the interest of 2-channel stereo listening, I felt that it was more appropriate here.

First and foremost, two-channel music is my priority. Surround is secondary to me.

I have been building/tweaking my two-channel system for years, and have arrived at a place that I absolutely love, which has my DAC running directly to my power amp.

I also plan to incorporate 5-channel surround (plus two subs,) with my two channel stereo rig serving as the main L/R amp & speakers, when in surround mode.

This has been a work in progress, and I have looked at many options, in how to integrate these two. I am leaning toward a high-end pre-pro that will handle all duties, rather than do two separate systems, via theater pass-through, etc.

However, my real challenge is finding the right pre-pro, which will not compromise the wonderful sound that I get from running my DAC directly to the power amp, for 2-channel music listening, which is better than 85% of the time.

I also would not mind if the pre-pro offered a quality room correction/speaker optimization, etc. But, again, not if it is at the expense of the magic that I currently have in my 2-channel rig.

I am looking for pre-pro recommendations that, in your experience, can pass the stereo source through, with no detectable loss or sonic changes.

I am not looking for a list of "xxx is a nice sounding pre-pro." I am on a mission to find a nice sounding pre-pro ***that will not compromise the sound that I have with my current 2-channel arrangement.***

The budget is not set in stone. But to throw a number on it, I'm expecting to be in the $10K +/- range.

I look forward to your recommendations.

Thank you.