I currently have the Denon 4306 in my home (temporary loaner) and I like the sound quality from it quite a bit. It delivers a solid full sound. It has decent features too, including 3 zones and a pretty fair lineup of connectivity options. However, it is only equipped with HDMI 1.1, and doesn't support 1080p or the new Dolby and DTS formats.
This past weekend I auditioned the Pioneer VSX92-TXI and the Denon AVR3808CI head to head. I listened to both units on their pure (direct) unprocessed setting, through a set of Viennas, no sub. The sound was very noticably different. On the Pioneer, the mids and highs were very bright and the lows were noticably absent - I mean there was no bass! On the Denon, the highs were a little bit muted, but the sound was much fuller. My wife was with me, and she even noted the difference and commented that the Pioneer sounded like crap.
For source material we used a variety of discs and DVDs, including instrumentals and vocals, and we also watched the nightcrawler Whitehouse scene from XMen. None of them produced a different result, the Pioneer was just lacking down low. Adding a sub helped it quite a bit, but it was still noticable even with the sub.
If you're limited to a choice between the two receivers and can't consider others, I would steer you towards the Denon. If you have options, I would look at newer models of Onkyo in your price range, they will have support for the newer formats, or raise your budget a little and consider the newer Denons.
EDIT:
I also wanted to add that Denon has released a wireless iPod dock for their receivers, which also enables you to connect to your wireless home network. Since network connectivity is on your list of desired features, I think you should seriously consider this. Also, so you mentioned a BR or HD player is in your near-term future, I would strongly advise you go to one of the newer receivers that supports 1080p. If you shop around on Froogle, you can find the Denon 3808 significantly cheaper than their $1600 MSRP (I see it for $1100).