Thanks, although speeds were horrible even when I was connected via gigabit ethernet to be honest (compared to copying to other parts of the network it was a LOT slower). Space is not an issue for me either as this is going to sit in the attic.
Well as Nightfox points out, for backup purposes the drives are fast enough even on USB. But if you intend to use the drive for other purposes, then yes it'll likely be rather slow through the AEBS and faster on the TC. And I guess the TC could always add more drives like the AEBS through the usb port, though those will all be slower. You might get better pricing for the storage going the AEBS route though.