My computer has got 6 connections (green, pink, blue, black, orange and grey). The pink is the microphone and the blue is apparently another Line In, but that leaves me with the Green, Black, Orange and Grey. My current speakers have black orange and green input, but I have never played around with that and just used green.
The reason you only get sound out of the right and left speakers is because thats all green gives you. black is sub and centre and orange is the rear 2(black and orange could be turned around, i forget and am just guessing).
you say you have s/pdif capabilities in everything that requires connections which is good.
There are so many options for sound systems its kind of hard to give you some direction
What you want is a set of speakers with an amp that has more than two s/pdif connections in it, and a lot of different settings to choose from. Different EQ's for watching movies and listening to different kinds of music. you also want the amp to do DTS because it is better than dolby digital.
As you have probably noticed by now the amp is the thing that really matters with audio.
all of these things will cost you about $400 and up
http://www.yamaha.com/yec/hometheater/yht.html?CTID=5000800They will be great quality sound and as a teenager of low income and loves music is what i bought.
You generally get what you pay for with speakers.
If your looking at just buying it for gaming then I would go with one of these:
http://www.logitech.com/index.cfm/speakers_audio/home_pc_speakers/devices/224&cl=au,enhttp://www.logitech.com/index.cfm/speakers_audio/home_pc_speakers/devices/3549&cl=au,enhttp://www.logitech.com/index.cfm/speakers_audio/home_pc_speakers/devices/234&cl=au,enhttp://www.logitech.com/index.cfm/speakers_audio/home_pc_speakers/devices/211&cl=au,enJust make sure which one has the correct inputs.