My Sonore server uses the SOtM USB outputs, which are fantastic. This server is much better than any of the Mac based solutions I tried (Mac Pro, Mac Mini, and Macbook Pro). It doesn't surprise me that Alexandre noticed a difference between the output of his Mini and Macbook. . .all USB is not created equal.
My MSB would sit behind a Trinnov ST2-Pro processor connected via AES/EBU. The source into the Trinnov is Offramp 5, which is fed by the SotM USB card in a dedicated PC based server (Caps 2.0).
In an ideal world, I would take the Trinnov out and use USB straight into the DAC, which would save me 10K worth of hardware. However, I keep finding the Trinnov if very effective in my system.
The key to the Analog DAC is that once you buy it, there's no opportunity for future upgrades. I'm not saying this is a bad thing. . .the DAC IV series just targets a different customer base.
If 10-11K is the absolute most you ever want to spend on a DAC that is a good thing; Matthew 6:13 "lead me not into temptation"