check this out :
they reviewed it to be very well off. it's got 5.1 surround in the form of rca outputs, a happy medium for direct connections to an amp or 2. if you check out the next page in on tom's hardware, it shows the software that comes with it. it's got the "4th" channel of the rca's for sub output and it looks like you can control the crossover (maybe?). if anyone's come across this tell me what you think. it's kind of pricey- @$119's the cheapest i've seen it at musiciansfriend.com, but not bad for a usb, freeing up one of your pci slots.
i've also checked out the other terratec audio cards and they have a 7.1 surround card with optical out built in. it's kind of rare to see a card that doesn't have a breakout box for optical out in the form of a pci card.