If you're look for something hotswappable, I would recommend a usb mobile rack instead, that can handle either serial or parallel ata. That way you can plug any normal hard drive you like in there while the machine is running. I've done this before and it works great.

You plug a standard IDE drive into the mobile rack, which is connected to the USB bus on the motherboard, and you can activate/deactivate/hotswap them just like a USB flash drive. It's worked for me with forensic analysis, I never had any problems with that setup.

Can't really recommenc any external hard drives, though, as I've never used them.