Question about DTS-HD

[volcomsocal]

I have an older Sony HTiB that I've been using as my surround sound setup that's connected to my 80 GB PS3. The HTiB is about 6 years old, so it doesn't have an hdmi jack but it does have an optical jack. So obviously I run the optical from the Sony receiver to my PS3. When watching blu-ray movies, I can choose an audio setup to listen to. Thing is, blu-ray movies offer DTS-HD, but not DTS. My Sony HTiB can't decode DTS-HD because it wasn't even around back when it was made... it can decode DTS though. So when I pop in a blu-ray, and I choose DTS-HD, what am I getting through my speakers? Should I choose 5.1 uncompressed instead, or am I wasting my time with either one? I really appreciate any helpful feedback.

And FYI - I'm not in the market to purchase an expensive surround sound system just so I can get the best audio possible (high-def audio). My Sony HTiB works just fine, and to be honest, it sounds damn good for what I paid.