One thing that still confuses me - so the modded Hiface comes with a 3.3V external power supply (batteries). This I understand but apparently the Hiface STILL needs the 5V power supply from the Mac for some other purpose. If you opt to purchase the modified USB cable that has the power line removed, or disabled, then you need to find another source for the 5V power supply which is in addition to the 3.3V battery pack.
Do I have this right? If so, then I wouldn't bother with the modified USB cable because according to what I am reading, this only "corrects" the final 5% of the sound quality being sought.
Cdm - Is this your understanding and what approach did you take? The modified USB or a regular USB cable and did not concern yourself with the last 5% of SQ?