I have a 320G internal HD on my I-mac with a 500G external HD which Time machine uses to back up. The 320G is almost full and I just pick up a 1.5T external. I would like to use the 1.5T external to store mainly pictures from i-Photo and home videos. What would be the ideal configuration? Should I just keep the current 500G external the way it is with Time Machine and just start storing new pictures and videos on the new 1.5T external? Any advised or recommendation would be appreciated.