Before you replace the DAC, see if it isn't the jitter from the Bluesound and transport that is causing this. Do both sources lack mid-bass?
Here is some typical jitter:
http://www.audiocircle.com/index.php?topic=154408.0
http://www.audiocircle.com/index.php?topic=154310.0
You might try a Synchro-Mesh reclocker in the S/PDIF coax cable to reduce jitter to ~20psec. 30-day money-back, less shipping.The Synchro-Mesh also has these sonic benefits:
1) Galvanically isolates the source from the DAC, eliminating ground-loops.
2) upsamples 44.1 to 96, so the digital filter used in the DAC is a better one, not brick-wall.
Also, I recommend to get a better S/PDIF coax cable, one that is high-performance like the Reference BNC with RCA adapters or the Standard BNC with RCA adapters. The Standard BNC is only $275.
Steve N.
Empirical Audio