I just ordered a new iMac 27. I got it with stock 8 gigs of ram and ordered two more 8 gig sticks from Crucial. Is there any problem with having 2 4gig and 2 8 gig (24 total)? I also got it with a 512 SSD. I'm currently using a 2009 24" and hope this new machine will show a big performance increase for my photo editing.