I'm looking for a sound card upgrade for my PowerMac G5. I want to get the best quality possible on a 50 -75 dollar budget. I hooked up my mini shelf system to my audio port in back. I used a cord that separates it into 2 L and R (red white). Am I already getting good quality as it is? Or could I use my mini shelf system plus a bunch of computer speaker with a 7.1 surround sound card.