I upgraded from the DMS-550 and I am about 140 hours on my new DMS-700 (ran the first 100 hours on a repetitive PSAudio burn-in CD). Daryl at Cary Audio has been awesome to work with. I have the DMS-700 connected to a T+A PA3000HV integrated amp with a PSAudio PW CD Transport connected to the DMS-700 via digital XLR.
I find, that the DMS-700 has an exceptionally natural sound signature with no sense of listening fatigue, especially compared to some of the equal or higher priced competitive products that I have tried in my system (Lumin and Aurender). Listening to my reference material on the DMS-700 reveals greater resolution, a larger more transparent sound stage with a wonderful analog warmth and smoothness. One area the DMS-700 excels is its ability to reproduce very heavy deep bass. The implementation of the AK4499EQ DAC chips (R2R ladder DAC) with FPGA technology has significantly improved the performance over the DMS-550.
Some great new features on the DMS-700 include the ability directly copy files over the network to the SD card and USB drives that are attached to the DMS-700. All in, I think Cary Audio has created an excellent digital source - streaming - pre-amp - DAC.