I'm going to be getting a 320GB drive (running out of room due to so many large RAW pictures). Anyway, I've been looking at the new WD Scorpio black which is 7200 RPMs. They also have the regular scorpio which is 5400 RPMs. Will I notice a big difference and is it worth it? It's almost 100 dollars more for the 7200 drive...should I just get the 5400 drive if I am happy with the performance of my 250GB 5400 RPM drive right now?