although we have different equipment and different setups i will provide my input...
I currently own a Marantz SR6003. Before this i owned a Yamaha RX-V3900 and Denon 2809ci.
In my comparisons i found the Marantz offered better performance than the Denon, and about similar quality to the Yamaha.
I found the denon 2809 lacked in its liveliness. Its was just so blah. But it sure was feature packed for the price point i got it at ($745). Now i know its a different model from what your looking at but remember its also higher up on the chain. Realize though, i do not dislike the denon by any means, i think its a fantastic unit.
The Marantz is also a different model than you are looking at, but the 6003 and 5003 actually don't differ much at all. The 6003 as a little bigger power supply, a usb input, dual HDMI outputs, a cleaner front panel with the metal door, and a GUI (but it does not overlay..meaning it exits out of the current screen to show the menu). I found it had overall a much better sound quality. My music actually had character and did not leave a bitter taste in my mouth like the Denon did. The Marantz is warm and intimate which is fantastic for its price class. It also has pre-outs if you ever decide to add an amp to give your speakers that extra oomph.
The downfall to the Marantz are the fact that it does not have the ability to set individual crossovers. There is only one global crossover point for all speakers. But this is not THAT big of a deal. I run my mains and center at large anyway. And leave the crossover for the rears. It also lacks the ability to apply audyssey to bistreamed DTS-MA and DDTrueHD signals. I found this to not be a big deal as i use a PS3 anyway and will not be bitstreaming the signals from it. So as long as you have a unit that will internally decode the new codecs, audyssey will still be applied. But also rememeber not everyone likes what audyssey does anyway so some people may never use it to begin with.
So take all this for what it is...my opinion. YMMV on anything you try, i just found that for the price the Marantz gave me all that i was looking for to satisfy my audio appetite

Good luck with your choice.