Recently bought a logitech z506 5.1 surround sound system to be used with my computer
my Motherboard (asus p8z77vlx) has 3 Audio related ports;a red/pink (sound recording), and a green and a blue, i'm guessing 2 channel audio?
I'm assuming i can't get actual 5.1 with these connectors. i'm currently using an audio in cable from the subwoofer to the green port on the motherboard so its emulated 5.1
Could i buy a cheap 4 or 6 channel sound card from ebay, and get 5.1? where would i connect the cables into? e.g. the ones below?
Certainly those speakers are good for the price but, if you take into account the Built-in controller unit, the speakers and the amp your cost pr item is only about $11 (US). Your on-board sound processor won't lower the quality of the final sound
It's also worth noting that your on-board sound processor is better than either of those two sound cards you posted a link to.
If you want to make a meaningful improvement over on-board sound you should be prepared to spend at least $50 (or your countries equivalent) on a sound card. Of course you would then need to upgrade your speakers to take full advantage of the better sound card.
Another-wards your current on-board sound and the logitech z506 are a good match.
As far as how to hook them up goes, just follow the manual that comes with your speakers. Each one of those 3 connections is for 2 speakers so you have the proper connections for 5.1.