The Griffen Firewave also doesn't support DTS. The Creative DDTS-100 is some what of a decent choice, it does DD and DTS decoding as well as just about all the variations of DTS and DD. But it's highly overpriced if you can still find it, been discontinued for a while, it's definitely not worth $140
You are best off just buying a digital set of speakers. But then you run into other problems, the availability of budget digital 5.1 PC speakers has dropped significantly in the last year or two. Altec Lancing makes a set that plugs in to USB (not a fan). And Logitech makes the Z-5500 which I wouldn't recommend to my grandmother, unless she liked boomy unnatural sound.
You are best off buying a low end Harman Kardon 5.1 receiver like the AVR-146 which is about $230, and something like some Klipsch Quintet II satellites (Vanns still sells them, though they are discontinued, I used to have them back in the early 2000's, pretty decent they look smilier to the Klipsch Promedia Ultra 5.1 but a big step above) or something along that lines. You can get away with a pretty decent sounding system for about $500 if you really shop around.
it really does sound amazing!
