Hello All, Another question about the iMac's RAM. I'm looking to purchase one next month and I'm planning on doing a lot of post production work for video. I had a chat with a guy at an Apple store, and his opinion was that I opt for the system with the higher video card memory (512MB) as opposed to going for the lower one at 256MB and later upgrading it's internal memory to 8GB. Which one am I actually getting more bang for my buck? Getting the 4GB system memory one and later bumping it to 8, or getting the 512MB graphics card one.