Hello... I'm thinking to buy a iMac and could need some advice what iMac to buy. I think I will only use the iMac for: Internet, Mail, light work with Photoshop and time by time XPlane and Call of Duty 4. I have the next options (first model about $170,00 less): 21.5" 3,2-GHz Intel Core i3 4 GB 1TB HD ATI Radeon HD 5670 512mb 21.5" 2,5-GHz quad-core Intel Core i5 4 GB 500MB HD AMD Radeon HD 6750M 512 MB Is there a big difference between these two ??