I had been planning on souping-up a 21.5" iMac (currently running a entry-level 20" 2008 iMac), after saving for some time. After seeing the 27" in the store, though, I'm a bit hooked on the idea of the larger screen. Aside from the typical uses (browsing, working in Office, etc), I'm a hobbyist SLR photographer and do a lot of work in Aperture (I do sell prints, but far from my primary source of income). Seeing as how the extra cost of the 27" is going to knock out some of my ability to upgrade the BTO, what should I be paying attention to first? Fusion drive is a must-have (I'm addicted to the SSD on my work laptop). I know I'll be doing memory 3rd party somewhere down the line. Does it make any sense to stretch and upgrade to the 3.4 i7, or is that money better spent towards the 680MX? Or is the 2.9 i5 with just a 660MX card probably "good enough"? I know *anything* I get right now will be light years ahead of my current setup, but I'd want to keep this system for a number of years... And it's been far too long since I've shopped to know how the systems currently compare.