If you use a Mac Mini late 2009 model, you can use a 16-foot USB cable with no impact on SQ. Buy it on ebay. Late model Minis have cable/USB port issues and do not sound as good IME.
If you want the best off-the-shelf SQ at 40 feet, then go with Logitech Touch wireless. It can be reclocked for even better SQ. Not as good as wired USB though.
Steve N.
Empirical Audio
If you want the best off-the-shelf SQ at 40 feet, then go with Logitech Touch wireless. It can be reclocked for even better SQ. Not as good as wired USB though.
Steve N.
Empirical Audio