My 320GB 5400RPM Fujitsu is getting full and slow so I'm going to extend the life of my mini by going for a bigger, faster drive. I was looking at either a WD Black (500GB or 750GB) or a Seagate Momentus XT 500GB. Not really wanting to put an SSD in due to cost/capacity constraints. The WD drives look the better value here. Any opinions?