streaming music via ethernet to receiver

The Denon will not stream directly from iTunes. It only works with Windows Media 11 or a DLNA server. You'd therefore need DLNA-compliant server software for your Mac for the Denon to be able to access the tracks on the computer. MediaTomb (freeware) might work. Alternatively. Twonky Media Server claims to be DLNA compliant, and Allegro says that their Allegro Media Server will be DLNA complaint "shortly". One of those, run on your Mac, would (at least in theory) then allow your Denon to access any tracks in the iTunes library that aren't copy protected.

If by "AirTunes jack" you're referring to the audio output, yes, that's probably easiest.

I also have the Denon 3808ci, and have downloaded the 30 day free trial of eyeconnect, which does allow me to access my entire iTunes (non-copyrighted) files and select them via the GUI nu artist, album, etc. I am having some problems with the Denon keeping the internet connection, however, but that was a pre-existing problem. I will likely buy eyeconect once the free trial is over.

On a related note, my network connection keeps getting dropped, and at times the connection is fine (the internet radio keeps playing) but the net/usb menu goes funny and the selection items become unselectable. I end up having to turn off the receiver and unplug the Airport express and replug it in. My network is an airport extreme, and teo airport expresses (one to use for airtunes and as a printserver, the other is dedicated to the denon). I tried a firmware update on the denon, but after an hour it was still on main firm, 1/14, and 00%. Any advice?

Thanks in advance.