They already said they were going to support 6.1 and 7.1 channel surround. And some games will support DTS and EX and above.
One game for the xbox I just noticed...Path of Neo is THX certified and it sounds great.
For people that have never heard games on digital surround, there is a major difference.
In Halo 2 on live I can hear people coming up a walkway behind me, with radar off. There is actually an extra zippy sound to sniper bullets flying by that you can never hear on analog stereo...swear to god.
It is just getting to the point where a bigger group of consumers have a digital setup.
You must realize that just having surround and a dolby reciever doesn't make the audio digital. You need the optical or coax coming from the xbox to the reciever to get the real deal. And the difference...is VERY noticable...say from phantom surround or Pro Logic.
I bet the first Star Wars game for the 360 will support DTS or ES at the software level. badass!