The FTW+ is more expensive by $40 when rebates are taken into account. While the backplate is nice, it's more optional than anything else and only costs $20 by itself. I don't think there's any conclusive testing showing the backplate makes too much of a difference in terms of performance. And it should be easy enough to overclock the SSC to meet the FTW+ performance levels as they have the same ACX 2.0+ cooler and power phases, according to the comparison chart here. I don't think the extra ~25MHz is worth the difference.
The Hyper 212 Evo is already more than enough to overclock the processor with. It's a very well proven cooler than can take the processor up to 4.6GHz at up to 1.4V CPU voltage. There's no denying that the Noctua cooler is even more effective at cooling and somewhat quieter, though. Eurogamer's review of the 6600K had them overclocking with the 212 Evo and they were able to reach 4.5GHz at 1.375V with temperatures just over 70 degrees at the worst, which is not bad. Better examples of the 6600K can overclock with lower voltages, perhaps.
The EVGA 650 G2 is a good power supply, but a bit expensive at $85. If you scroll down at this link to see the price tracker, you can see it has dropped to $60~70 in the past few weeks. The EVGA B2 is a bit better for price to performance and has also been reviewed with high rating. there are other choices as well, I see the Corsair RM650 (gold and fully modular) and the Antec HCG-850M (bronze and semi-modular), both $70 after $20 rebate.
Besides, Xion_Stellar said the parts list was a bit too expensive and needed to keep it at $1200 or under, so naturally he has to go with some cheaper parts to help keep the price lower. As far as I know, there's nothing horribly wrong with the part changes, and nothing that should be avoided.
