I have the 8600..You have to make sure your amp can take 6.5volts...thats quite a bit, and not every amp is designed for that. Of course it will be a cleaner signal, but like someone said, you have to figure out your amps input voltage range before you buy.
I love my 8600 though, its awesome. I use the AUX input to run my port. DVD player so I hear the DVD through my speakers, thats an awesome feature. You can make your own videos (but you have to make them from a single picture, I used a picture from Scarface). You can make your own backrounds. And its very nice to go through menus. You dont have to keep clicking the same button to run through menus, its all the multi-function knob and the display makes it feel like you're running through menus on a computer.
I'd go Pioneer 860/8600. Depending on your amps input voltage range.