If it's any help, don't build now. Wait till next month or April for Sandy Bridge. Here's a comparison of what you'd be getting performance wise. 2500K = 230$ USD // 950 = 280-290$ USD.
2500K vs i7 950: http://www.anandtech.com/bench/Product/288?vs=100
Conclusion: Basically the same, you save 50$ at the least, and in some cases getting WAY better performance. Load temps are lower, power consumption is lower. Overclocks are way higher. 32nm = win.