hi everyone one !!! just picked up my imac 27 15 2.7. im in heaven. good bye pc. was wondering it came with 2x2gb sticks of ram. i would like to think i could benefit from more ram. running aperture, final cut pro typical apps and web. can i keep the 2x2gb cards and add 2x4gb sticks or do they all have o be matched sizes? that would make for 12gb of ram that should be sufficient? i dont think 16gb is really necessary. is there a difference in ram manufacturers? thanks everyone !!!!