Had the 4002 , am getting the 663
In a nutshell:
Slightly more power than the Marantz, 1 less HDMI input BUT true hd, dts hd, etc for sound and Deep color for vid, 1.3 switching/repeating, upconversion to HDMI, more flexible bass xover settings, and some other things....
I'm getting this instead of the Marantz, since I respect the Marantz brand but this receiver has all I could want for about the same price.