OK, just wondering now.
Surely a dac with volume control and some sort of filters (like tone controls, I need to turn the bass down a notch and raise the treble by one too) to adjust the sound would do the job given that I only need the one digital input?
I had an RME dac a few years ago which was way to complicated for me to ever work out where the filters were but might this be something to look into, should I start a 'What Dac' thread.....?
For what it's worth, my system is a pimped bluesound node streamer into an old rega dac, then into a quad 66 pre (mainly for the tilt and filters and remote) then on to my power amp.