I'm in the process of setting up a Venus T4U made by AMS electronics. $150 at Fry's. It holds 4 drives up to a total of 3TB. USB 2 and it's for ATA drives only. If you go to the AMS website I think you'll find the same rig for SATA.
I try to buy OEM HDDs which are a lot cheaper than the retail drives. Only difference is that you don't get cables etc. but you don't need those if you're putting them in a case.
I am currently using 2- Lacie 400GB FW800 externals and a 200GB Lacie FW800. I use 400A as my primary and 400B as a direct backup. The 200 is used as an archiving drive to keep track of waht images need to be burned off.
I am having lots of copying type errors with the Lacie drives and have had to replace the power cords many times. I am outgrowing the system and if forced to invest in something that will take me farther, that is what I am lookign for. 1TB of space as a primary with anoth to direct backup? Ideally something modular would be nice??? I have a MacPro with 5GB RAM and it is a dual 3GhZ (quad)machine. I feel things should operate much quicker with this horsepower as I have very few apps on it. The 400B drive takes a minute or two to show its contents in the finder which is not right.