New sound card or speakers?

[The Mad One]

I currently have an Audigy 2 Plat Ex which has connected to it Creative Megaworks 2.1 and then a rather old but semi decent stereo for the rear 2 sepeakers making it a 4.1 setup. I now have all my speakers set up really nicely but I'd like to upgrade my sound even further, but I'm not sure what I would benefit most from, an Creative X-Fi Elite Pro or the Logitech Z-5500. Any suggestions? In time I will upgrade both but I only have enough money for one at this time.

 

[The Mad One]

Well I do need the extra connectors hence me already having the platinum version of the Audigy 2, plus I already have some medusas 5.1 but that wasn’t the original question. One of the problems is that there’s a quiet static type sound coming out of my back stereo speakers. It’s hard to tell what’s doing it whether it’s the stereo itself or the sound card since when my pc starts up the static sound comes out of all the speakers until windows starts up and loads the sound card drivers, which I find really odd.

So the original question what does everyone think would benefit me most based on my current set up? new speakers or new sound card?