Well you end up spending an extra $400 ($200 for the upgraded 27 and $200 for the processor) for it so my thinking is why not save that money and probably in another 3-4 years put that towards a new one. My best guess is you'll get a max 25% increase in CPU speed with the upgrade. From the last gen iMac to this one you're looking at a 25% increase in processor overall and some benchmarks I believe showed up to 100% increase. So if you use that as your "upgrade path". Then over the course of 3-4 years you get more value for your money there. I have no doubt the stock 27" iMac will be plenty fast and will be a huge upgrade from your current system.photo and video, by the biggest and fastest of everything....I think this negates a valid price vs performance analysis. I just ended up building a hackintosh last night because the 27" iMac is out of my price range and the 21" is pretty much not upgradable at all unless you have apple do it which is super expensive. I think the stock CPU will be fast enough for you. Graphics card won't make a huge difference either. These are all incremental upgrades. The fusion drive though might be worth it. I made my own fusion drive since it's a hackintosh and it only cost me $75 extra. I think apple charges $250 which isn't cheap but for apple standards isn't bad. The only way to do this on an iMac if you don't get it with it is to setup a thunderbolt SSD and by that point you're better off just getting it from Apple. That's my take on it. So from Apple, possibly Fusion drive and then upgrade the ram your self.
Thanks. So you feel the stock i5 on the 27" is good enough. What is the advantages of i7 then?