By all accounts, the Denon 3500 is more in line with the Marantz sr60xx series, If I Recall Correctly.
I would be more inclined to put my money at that level of device, than anything lower on the pole.
Oh yeah... I did!
The 6012 from Marantz has been pretty solid. Mine came with a hard-to-diagnose problem in the video board, but I got it taken care of under warranty and it has been fine since.
Make certain the Denon has all the features/connectivity you need... I think it's the smarter purchase, if it has the features you want.