The budget is somewhat flexible. 800 is ideal, but basically I know I won't be updating my processor and Mobo for at least 4 years, and I want something that is future-proof for that entire period. If I go up to 1000, I'm still ok with it.
Absolutely nothing that you buy today will be worth keeping in 4 years. "Future-proofing" is impossible, so just get that silly idea out of your head.
I agree with everyone else about going 1156 i5. Muskie's build is pretty good, though I would probably get a dual-channel kit. At your budget, just grab a 1TB F3 for $75.