I've had the SR6004 since the end of February and I'm very happy with it. If you haven't already, you might want to take a look at this
review from Audioholics. The Marantz had all the features I need, a good amplifier section, and I could get it for a more reasonable price than some of the Denons, here in the Netherlands.
That said, many others on this forum are very happy with their Denons or Onkyos. I would concentrate on getting all the features you want without spending a fortune. As for the Marantz, keep in mind that it cannot apply Audyssey to bitstreamed HD audio (but it can
if your blu-ray player sends it as LPCM) and video upconversion, from what I've read, is mediocre. (But, again, if you let your player do the upconverting and decoding, not an issue.) I'm not sufficiently familiar with Audyssey to comment on the differences between MultEQ and MultEQ XT, but that might be one reason, for some, to prefer the Denon 3310 over this Marantz.
In the end, if all else is equal, and you still can't decide: pick the receiver you think looks prettiest. I know I did.