The ReadyNAS NV+.

The only other thing that is holding me back it the fact that I use a D-Link DGL-4300 wireless router which, as far as I can tell, doesn't support Jumbo frames.

Since this D-link is one of the best routers I've ever owned, if not THE best router I've ever owned, I'm not really inclided to swap it for something else. Besides, I've yet to see the first router that is wireless, has a 4-port gigabit switch built in and does jumbo frames, all combined into one device...

The speed difference that is mentioned on the infrant forums almost makes it worth it though... almost...