Hi I am thinking about buying an iMac in the next couple of days.. I am limited to space so was thinking of getting the 21.5" iMac with i7 Possessor. Is there a big difference between the 21.5" and The 27" iMacs with i7 Possessors? Also I hear that the i7 has hyper threading. Is this the case for both i7 processors or just the one in the 27" iMac. Would I benefit alot from getting the 27" iMac i7 over the 21.5" i7 as I do alot of video editing and music production. Any advise would be greatly appreciated.