Check it out: Momitsu 880N.

Built-in ethernet port so it can play MPEG-1, MPEG-2, MPEG-4, OpenDivX, Xvid, etc. digital media files over the network. It requires some server software, but it's available for Windows, MacOS, and "Linux/Unix". And it's "only" $379. Oh, and it plays DVDs and has a DVI connection and will upconvert DVDs to HD.

Sounds snazzy, but I don't have $379 lying around.