Judging by the lack of a Firewire port and having an audio in AND an audio out, your Laptop won't push audio out through a MiniDP to HDMI dongle. Here's what I use for my MBP, and it works great.
Kanex iDapt HDMI
Works like a charm and is only 4.70
RiteAV - 3.5mm to Stereo RCA Male Cable - 6 ft.
Works great, is cheap, and gets the Audio to the TV. With shipping, this is all around $10.
I'm assuming you have an HDMI cord, but if not...
HDMI to HDMI 6 Foot Cable
$2.28, and works fantastically. No need for anything more expensive than that, as they all work the same.
Plug the Minidisplay port end of the dongle into your computer, plug the of the HDMI cord into the Dongle, and plug the HDMI cord into your TV. Then plug the 3.5mm Headphone jack into your computer, and plug the two RCA ends into their respective colors under HDMI1 In.
I use this same setup to play WoW, watch TV shows, and it's beautiful. Have fun!