I'll post a picture of my DTS decoder thats in my trunk next to my amps. Has Toslink, Coaxial and Analog inputs. Has crossovers and phantom center channel adjustment. It also has a remote volume control that I mounted nicely next to my fog light, intercooler switch.
Right now I am using the Toslink with the Sound Blaster NX2.
Before I had the Decoder, when I played my Dlink USB FM and put it into the Line-In on the NX2 it would only play out the front two channels. After getting the decoder, the line in now plays over all 4.1 channels. (I don't have a center)
I got it off eBay from some guy in Hong Kong. It was $360 shipped. I'll post pics later.