You might be interested in some new NAS hardware that has recently been released.

D-Link have released a NAS unit called the DNS-323 which comes without any drives so you can put whatever you like in the unit. You can get 2 and 4 bay units and it takes SATA drives.

An alternative is a new unit from Linksys called the Network Storage Link. You can connect any external USB drives you have to it and they are then instantly shared on the LAN.

And lastly Buffalo have released a new version of the TeraStation, called the TeraStation Pro II 2TB which is meant to me much faster. The review I read said it managed to transfer 1GB of data in 90 seconds, which seems quite quick.