Well, given the PS3 only has an HDMI output for HD audio, this is the only way to hook it up to the Sony (optical can't handle HD audio on any system as it doesn't have the bandwidth necessary). I can't answer from experience on the Sony, but from what I've heard, the Sony would definitely run the 685 system - it may well not use it to its full potential, but if you can afford it, isn't it nice to know, when you save some money in the future and get a new amp, you'll benefit?!