I know the Denon models have a loop from the pre-amp out to the main-in for the amp. All you have to do is get some rca y-connectors to split them. That is what marantz(Denon) support told me.
Look at the last post in this thread I started:
http://www.hometheaterforum.com/htfo...ighlight=denon
There are pictures of the rear of the denon posted in there also that show what inputs/outputs I am talking about.