Multimedia: Dell Inspiron as HTPC?

Dell Inspiron as HTPC?

I recently purchased a Dell Inspiron 518, running 64 bit Vista Premium. It's a refurb, one 'bonus feature' is the 256MB ATI Radeon HD 3450 graphics card, which has an HDMI output. I wasn't intending to use this as a HTPC, but now I'm wondering if it's as easy as just running an HDMI cable to my Samsung 50" plasma (720P). I've read a bunch of posts, one issue seems to be audio. Will the HDMI carry 5.1 surround sound (routed through the TV to my home theater)? Sorry if this is a noob question, I have looked around quite a bit and seem to get conflicting answers.

Also, any other general advice would be appreciated, I think I've figured out that a TV tuner card is no real use to me (I have satellite and don't want to mount an antenna on my roof), and I'm not satisfied with just using my xbox 360 as a MCE (don't seem to be able to play backed up dvds from my hard drive to my TV).

Any and all pointer/ advice/ thoughts are appreciated!