I've done a lot of research a while back about the 640gb 6400aaks (blue line, black is a smudgen faster) and the 300gb Veloci. I first purchased a Velociraptor back when it was $300 and didn't think it was worth it and was happy with the 640gb. That was before I got my mac pro and realized it's worth spending some money (and back when I didn't have a lot of extra spending cash). I might have answered the questions myself, but I had to see if any other users have tried this: I recently did a RAID0 of (2) 6400aaks drives, and currently getting 210mb/s+ on both read and write. Now, this is my boot+apps drive only. Honestly, I really couldn't tell a difference from my previous setup as a single 6400aaks drive as boot. Since the RAID0 is taking up 2 HD slots I wouldn't mind freeing up a slot if the 300gb Velociraptor will be as fast or faster. I know it maxes out around 115mb/s, but the seek time is going to be much better. Considering I don't need hugely fast read/write times, will I notice a difference or will it be negligible?