I was looking for some good 5.1 speakers that had an optical input on them to use for both my 360 and gaming pc and I found someone willing to sell me a set of z680s for $150. I listened to them and they appear to be in excellent condition. Is this a fair price for them? I currently have the z5300s and I know the 5500s also have a digital decoder on them. I think the z680 were from a generation prior, but I'm not quite sure.