I have a MBP Santa Rosa, I decided to upgrade the RAM from 2GB to 6GB. So I need a 2GB and a 4GB memory card. I barely find 4GB RAM in my country which is not in a kit. There is a large selection for the 2GB though. The best option looks like would be a Corsair 4096MB 800MHz CL5 DDR2 - VS4GSDS800D2 and a GeIL USA 2048MB 800MHz CL5 DDR2 - GX2S6400-2GB I know my laptop only works on 667Mhz, and these would work only on 667Mhz, but I couldn't find any 667Mhz 4GB memory card, and the 800Mhz ones usually cheaper. Would these two work together? Both CL5 (I'm not sure what it means), but the Corsair is 6-6-6-18 and the Geil is 5-5-5-15 Is that a problem? Please let me know what are the most important specs they have to match.