Just wanted to share a little USB device that will enable any Mac to send multichannel (AC3/DTS) audio to any 5.1/7.1 speaker setup (I have analog 5.1) - the Encore ENMAB-8CM 7.1 Channel USB Audio Box. Why does it need to be known? Because as far as I know it is the only USB audio device that is a native plug-and-play multichannel USB audio device that is compatible with Mac OS X (tested only on an rMBP with 10.8.4 - but Mac OS X is NOT officially supported!). And while there may be other solutions out there, I'm pretty sure they're not worth ~$20. Yup, it's that cheap probably because of the chipset used (C-Media CM6206) or probably because they're not big on support (nor with packaging). I have no way of measuring SNR (etc.) but for non-professional/non-audiophile use (games, VLC, multichannel music) I'd say it's perfect for the price. Aside from a slew of analog input/output sockets, it even has 2 sockets dedicated for optical in/out (untested!) - and it's bus-powered. All I can say is I'm very happy with it and I'm pretty sure someone out there is looking for something similar to this, especially those on unsupported hardware. There are a few other C-Media CM6206-based devices out there that are fairly similar to the Encore ENMAB-8CM like the Terratec Aureon 7.1 USB but cost more or vary in shape and/or layout. They may or may not work natively with Mac OS X - there are no assurances but please feel free to report your results/experience with it.