I'm switching from Windows PC to Mac (and from reflex interchangeable lens cameras to mirrorless but that's another story). I'm considering one of those new 20.5" iMac boxes with LED display. That particular size comes with two config options -- the lower priced one has 500GB HDD and GeForce 9400M graphics, while the higher priced one has 1TB HDD and Radeon HD 4670. The larger 1TB storage is nice but not quite worth the upgrade cost by itself, considering I can add another USB HDD at much lower cost and with marginally compromised wiring/asthetics. What I don't know is if the Radeon HD 4670 graphics will offer any substantial benefits over GeForce 9400M. I will mostly be working on RAW image processing and output for prints. The files will include raw files from various cameras and also 5400DPI linear TIFF scans of 35mm film that are typically 250+MB in size. I will also likely install Windows 7 via BootCamp. I wonder if the Radeon HD 4670 will offer any significant benefit for above type of work -- significant enough to justify the cost differential. Your thoughts?