The U3 may "work" with OS X, but I'm assuming it doesn't add DH processing to multichannel audio, right? And that's the whole point of it, though it sounds like you have few Mac games... The Mac App Store and Steam catalogs are growing, FYI. I prefer Starcraft II in Mac, fewer bugs it seems (played HotS on PC, got weird shadows and looping audio), and some steam games if you buy one copy of the game, you can play it on either system (Like SW: the force unleashed. Weirdly it downloaded like 10x faster too).
Glad you're enjoying the E12! At some point people thought it's purpose was to be a bass machine, which is odd, but as I'm sure you're experiencing it's more about overall improvement and enlivening. I agree that the K701+amp is not a wholly 2x better experience than something like Koss KSC75 straight out of an iPod (listening to Calexico that way right now), BUT... don't you prefer it this way? Lol. Get used to it, and it'll be HARD to go back!
And yeah, the Recon3D USB + E12 + Q701 was good enoUgh for me, lol