I have a ready nas NVX Pro (4x1TB disks, currently 3 in a raid 5 with a hotspare) and its data transfer rate is superb, easy to set up, runs linux so you can add media servers to stream to the 360, bit torrent clients etc, remote access over the internet as needed. Its perfect for me in all but one area, the fans are too noisy. I can hear it anywhere in the house, even when its on power save. Its louder than my old poweredge 2950.
I would be careful of the netgear ready nas boxes as that does seem to be the must grumped about thing on the support forum, noise!
David.