In the end it comes down to what you want to do with it. If you're not an overclocker, and you're doing normal things (i.e. gaming, webbing, running productivity and media apps, etc.) either chip is equally fine. Haswell has more future upside if AVX optimized software takes off. But it will probably be a a bit before it does - assuming it does. I'm thinking it will. Eventually...
Prices being mostly equal, having additional features that may take off down the road, and performance being marginally better with Haswell across the board, Haswell is technically the more "future-proof" chip. But seriously, who cares? By the time the software catches up, it'll be time for a new system anyway.
I think your current build configuration looks just fine. It'll be one serious machine once it gets assembled. I wouldn't worry about it.
Simple truth is this technology advances so quickly, and changes course so rapidly, that no matter what you pick today
- it won't be the ideal decision a year from now. My approach is: get a decent CPU, a quality mobo, name-brand power supply and video card, max out the RAM, add a quality hard drive - and call it a day. And no matter what else, try not to let it make you crazy.