I'm considering getting another hard drive as I'm battling with space on my current one. Thing is, I have an iMac, so I can't just add another internal drive or replace it. So, it's going to have to be an external hard drive. I'm a bit concerned about transfer rates, though. I'll definitely be going for a firewire 800 interface and it will mainly be used to store downloads but I'm aware that external hard drives are slower (well, it's not the hard drive that's slower, it's the interface) and am wondering if it would end up being a hindrance. Theoretically, it shouldn't be THAT bad. 800mbits/sec works out at around 100mb/sec which is pretty good. I'm not sure how that relates to internal drives, though. Also, let's just say that my internal hard drive broke down and I had to use my external hard drive as the main hard drive, would it be a viable alternative?