Spec me... sound system or decoder for PC+360+TV

[Crowze]

I've only had my 360 for two days and already I'm looking at how to improve it . The main limitation I've got at the moment is using the bog-standard analog jacks for audio, whereas I'd like to use the digital 5.1, but I'd also like to rig up my MythTV box to my main speakers instead of using the rubbish built-in ones on my monitor. Here's what I've got:
PC + X-Fi Platinum
MythTV box + Audigy 2
Xbox360
Creative Inspire 6.1 6700

At the moment I'm using 5.1 analog outputs from the x-fi into the inputs on the 6700, and also using a splitter on the front input to connect the 360. Ideally what I'm after is a decoder box like the Creative DDTS-100, but I can't find it anywhere apart from the Bay where they go for ridiculous prices. The alternative is to get the Logitech X-5500 set, but I don't really want to spend that much and I don't think my room is big enough to accommodate it, let alone warrant 500W+. Does anyone know of any alternatives I could go for - either a smaller speaker set with a built-in decoder or a standalone decoder box? Just the product name will do, I can usually find out where to buy it myself .

 

[Crowze]

Well, the issue is more about the physical size of the speakers rather than the power output. I'm looking at the 5500's because they have multiple inputs and are generally far cheaper than getting a full-blown AV system. Ideally what I'm after is the Creative TD-7700 system which includes the DDTS decoder, but as usual they go for crazy money on the Bay - almost as much as the Logitech set. I have a feeling I'll have to save a few pennies, tidy my room and get the 5500, unless anyone can suggest an alternative.