Oh, and in case you're wondering: yes, the faster CPU is the Lynnfield i7 870 with it's clock rate of 2,93 ghz. Yes, the Bloomsfield i7 Extreme 975 has a clock rate of 3,33 ghz, but in this case, that does not make it faster. The keyword here is Turbo Mode.
They both have turbo enabled, but on the Lynnfield, the turbo is far more potent. So much more, that they actually both turbo up to the same speed, being 3,6 ghz.
The Lynnfield however, runs alot colder, which makes it able to utilize turbo much more. This is the final factor, which makes the Lynnfield 870 the (by a small margin) faster CPU.
One limit though: The 1156 platform, which the lynnfield is on, has less PCI-e lanes available, making it inferior in a multi-GPU system.
So ultimately it comes down to this: are you willing to pay about twice as much in order to have more PCI-e lanes available?