I was just listening to them today doing some comparison shopping at Best Buy. They have the Z560s, Z680s and the Promedias all set up next to each other now, which is pretty convenient.
The 560s, in my opinion, have some good heavy bass, but it gets a little more muddy than the Promedias. You also don't get very good highs with them. I think the whole setup is really too dominated by the woofer, with the satellites being a bit underpowered. To me, buying the Promedias gets you a better woofer, much better satellites, and a center channel to boot. I think it's worth splurging on, but if you can grab the 560s for $250 less, that seems smart to me.
The 680s weren't working right when I saw them, so no sound. I can say that I was somewhat disappointed with the well-reviewed control panel. The LCD isn't very bright or visible, and the controls aren't as intuitive as the Promedias. The big selling point is still "free" Dolby input, which I assume works just fine. I'd like to hear these before recommending them, but the Dolby alone is probably good reason to get some 680s if you want to go for something more expensive than the 560s.
<P ID="edit"><FONT SIZE=-1><EM>Edited by letdown on 12/29/02 11:08 PM.</EM></FONT></P>