i'll tell you all i got this set up but a little better lol and if plan to run two cards u need to go liquid cooling i've lost a card recently to the overheating.
corsair Obsisidan 800d case
Sabertooth x58 board
twin asus NVIDIA GTS 250 1GB video cards
24gb of Corsair vengeance 1600MHZ ram
3 X 1 TB seagate sata 2
1 X 1 TB seagate sata 3
2 X 750 GB seagate sata 2
1 X western digital 300gb 10000rpm sata 3
Corsair airflow plus Ram cooler fan and the Corsair hydro h80 liquid cooler looking to liquid cool my video cards now and maybe the board as well got enough space in the 24" tower what a beast
I just spent 10 minutes summarizing this link for you and I accidentally closed this window instead of the tab. Sorry but you will have to read through it. It is a very informative guide to overclocking the i7 920 which is the same for your i7 950. Use msi afterburner to overcock your gpu. It is very easy to use and free.
The guide does not tell you this.... The stock voltage range of your cpu is 1.1 to 1.375V. In this range is safe for daily use. The absolute max is 1.55V. Beyond this will seriously degrade your chip fast. The max qpi is 1.355V. Again it is not recommended to go beyond this but many use qpi voltages of 1.4V and higher with no problems.