I originally agreed with all that have suggested pairing a good quality tube preamp with their class D amps. For a few years I used a VTL 2.5L preamp, with the four standard tubes swapped out for a set of four NOS (new old stock) Mullard tubes in my combo 2-channel music and 5.1 ch surround system for HT. The HT portion of my system included an Oppo 105 Bluray player and a Parasound AV-2500 5.1 surround sound preamp/processor. The VTL has a HT passthru switch and the Oppo is able to play CD, SACD and DVD-A discs and hi-res music files for 2-ch audio as well as DVD and Bluray video discs for HT.
This setup sounded great for music and HT and I never thought I'd sell the VTL tube preamp. But I had an urge to streamline my system and I tried my system out without the Parasound surround processor and the VTL. I just went direct from the Oppo's outputs to my amps; a pair of class D D-Sonic M3-600-M mono block amps for l+r stereo for music and front l+r channels for HT surround, a bridged stereo class D Emerald Physics EP-100-SE amp for the center ch and a stereo Class D Audio SDS-440-CS amp for the rear surround channels.
The Oppo's audio sections are very high quality with a detailed and neutral presentation just as all of my class D amps are. I expected the combined overall sound to be too sterile, neutral and lacking in dimension, warmth, bloom and body. However, I was surprised to discover that all my familiar music sounded just as sweet, warm, dimensional and full of natural body without the flavoring I had assumed the VTL and tubes were providing.
I think it's important to point out that these very good results were obtained on music that was well recorded. Fortunately, most of my familiar music turned out to be well recorded but, unfortunately, not all of my music recordings survived such close scrutiny of quality. There are some recordings I've removed from the rotation if I was unable to find a well recorded example of the same music.
These were unexpected results, somewhat proven by the fact that I had just bought and installed a complete four tube replacement set of $200 NOS Mullard tubes in the VTL. But I felt I had to trust my ears, so I removed the VTL from my system and sold it to a buddy.
My new system configuration, combining an accurate, detailed and neutral preamp with amps that have the same characteristics, not surprisingly delivers an overall system sound that is very accurate, detailed and neutral. I related my experience just for the benefit of those considering class D amps. My main point being you can obtain very good overall system sound quality using class D amps by either pairing it with an accurate, detailed and neutral preamp (usually solid state) along with exclusively well recorded source material or pairing it with a more flavored preamp (usually tubed) that is more forgiving on poorly recorded source material. A choice of two methods reflecting different personal preferences.
Tim