Okay, here's my suggestions.
Are you really, really that into AMD? Because, in my experience, Intel procs are a lot better and more compatible with the latest graphics cards. Besides the fact that getting a 955 is silly, as you can just overclock a "lesser" model (one that has the same architecture, but with a slower clock speed) to the same speed. But, as you can see from the price of that 955, I don't think that getting a slower model is an option. After all, you get what you pay for.
If you go Intel, try looking at a good Asus motherboard, and get the i7 920. It's 250$ (250$ and 750$ less than the 950 and 975, respectively) and has the exact same architecture as the 950 and 975, with a lower clock speed. I "overclocked" mine right up to the 975's speeds (from 2.66ghz to 3.2ghz) without even increasing the cpu voltage. That's right, I never had to increase the cpu voltage, or the voltage of anything else, for that matter.
And, if you go Intel, make sure that Asus motherboard is compatible with the X58 chipset. Also, get 6Gb of RAM. X58 really uses triple-channel memory well, and you should really take advantage of that. It'll be about 50$ more to do so, however.
I suggest that you set your budget at $1000 and try to fit these suggestions in. If you are an AMD fan, by all means, go for it, but IMO, Intel is better.
