The big difference between the Z-680 and Z-5500 is in bass performance. The new 10 inch subwoofer used by the Z-5500 is a lot more efficient and can play a lot lower than the 8 inch unit used in the Z-680. I had very little complaints about the Z-680 8 inch driver, but the 10 inch unit of the Z-5500 is downright incredible. When corner loaded, the Z-5500 subwoofer produced bass that was noticeably deeper at higher volumes. You need to be very careful with the bass control or you'll completely over power the satellite speakers.



Link: TTZ