"The Digital BA7500 is a digital only system, and requires a properly set up digital sound card."
Also, according to the spec link those appear to be only 4.1; you need 5 full range speakers and a sub for true 5.1 output.
A center channel , a front L & R, a surround L & R & sub.
There is also no mention of having any decoder built-in, but that they are digital ready, which doesn't mean too much in the speaker realm; I think that quote from their site above means you need the card for the decoding, I might be wrong.
BUT, if you are wanting something for some home theater or small satellite setup, this is not going to do what you want.
Although I am not a fan of all-in-one boxed DTS/DD solutions, you would be better off going that route over this one IMHO. It will be expandable in most cases, true DTS, DD with sound fields, more flexable, better clarity and channel separation, and much more power.
Like the: Philips HTS3400/37B $129
Search Target, Costco, WalMart and pawn shops... or look to updating to a nice A/V head unit that will last and provide you with numerous features.