Digital 5.1 speakers

Hi guys. I'm a student studying in the Uk and i recently got me a semi-decent rig

P4 3ghz wit EM64T with 2gb or Kingston Value RAm 22r3 667Mhz.
It's mobo is a Gigabyte Nforce4 SLI Intel Edition.
As it has Spdif out, i was thinking of getting me a set of digital speakers.

Now, personally i don;t know much about speakers but my old Altec Lansing ATP3 were decent. I want to step up to 5 speakers but dont have the money and the availability of Klispch's and Logitech Z5300s.

I was thinking initially of the Logitech X530 and the Inspire 5800 theu ebay.uk and thought i would buy a cheap 2nd hand Audigy2.

But someone convinced me that i should get a set of digital speakers. Know i know the higher end Megaworks and Logitech are digital but its way out of my budget. I have about 40-50 GBP. I was thinking of getting the Creative Cambridge 580 as it's available on cheap from ebay. I know it has a sucessor - Inspire 5700 Digital but its not available for that price.

Those are my ideas so far. I was wondering if u audiophiles can teach a noob here on what to get.

I will be mianly watching downloaded movies, watching streamed sports channel on it and quite constantly listening to mp3 and ocasisonal CD music. Beause i have a EVGA turbo edition 7900GT in it, i am by default required to play some games to get my 160 pounds worth of it but i have to say i would put gaming as the last in the list of things i will do most with the speakers.

Oh great gurus. Do enlighten me.

Which do i get? Or any other suggestions?