If your Mac doesn't have optical audio out, you can still enjoy Dolby Digital 5.1 surround sound from your system. The Griffin FireWave is a firewire connected breakout box that delivers six discrete channels as 1/8″ mini jacks. These in turn get connected to your amplifier and then to your speakers. This unit is great for quick impromptu setups using existing desktop computer speakers. It works with DVD Player, VLC, and even Traktor DJ Studio where the 3 pairs of stereo outputs can be assigned to headphone, main, booth or record.
Best of all the unit is currently $29.99 with free shipping.