You can, through one of the two audio out jacks.
See page 16 of the User's Manual (available on-line, but not in the box) to connect an audio device. For Surround Sound, you'll want to use the Optical/SPDIF Out Jack with Cable, and connect to your A/V.
See page 27 for Avanced Audio Settings. You'll want to set the Digital Audio Out to Dolby Digital.
Sometimes, these "pass-through" audio connections do not always work - for a number of breakdown reasons. If it doesn't, and your MAC is equipped with an Optical/SPDIF Out Jack or Coaxial Audio Out, then connect directly to your A/v system without the TV pass-through.
In the end, you may need to use the pass-through and still may not get a true 5.1 or 7.1 Surround. However, if your A/V system is equipped with Dolby ProLogic, that can simulate the Surround Sound.
Best of luck.