Okay I am new to Mac's never owned one and was gonna buy the 21.5 with terabyte harddrive and upgrade the processor to an i5 but I heard a lot of the 21.5 have the yellow tint problem, do these new ones still have this problem and how much less common is it with the 27 inch one. So since I might get the 27inch I will not have enough to upgrade the processor so at a later date can I open her up and drop an i7 or i5 processor in it? Also why can't I choose to upgrade to an i7 on the other iMacs except the most expensive 27 or is there a way?? So let me know about the yellow tint and processor stuff and all my questions thank you