From what I've read concerning 5.1, there's no difference between the previous Live versions and the current 5.1 versions. They just bundle software to decode the AC-3...it's not hardware decoding. Anyone using an older Live still has 5.1 with the proper DVD player that decodes AC-3.
I just got an X-Gamer 5.1 for 79.95 at Best Buy last week (don't bother rushing down...it was mismarked on the shelf, and they honored their mistake for me). I've scoured the manual and the site looking for an answer. Nothing on the site that I could find. In "Advanced Configs" of the manual, they only give specific instructions for a 4.0 connection to an AC-3 receiver or four-point sound system, and how to connect an MPEG hardware decoder for 5.1 on DTT, but they fail to describe home theater systems. Even on the page specifying how to hook up the optional I/O card sez nothing about hooking that digital-out to an AC-3 receiver...they don't even explain whether or not the I/O can connect to the DTT, only "recording to digital devices".
But on page 11, they "elude" to the fact that the Analog/Digital Output jack will deliver the software-decoded AC-3: "...you will need a seperate 3.5mm-to-RCA jack cable to connect to your decoder".
Funny how Creative plasters the manual and their site with "home theater", calls all of their new products "5.1", and then doesn't give concrete details on how it's done, or even as little as how to do the hook-ups with their cards...they only push their DTT, over and over again.