Comparaing 2 CPUs

I would like to know which of this CPUs is better

Intel Core 2 Duo E8400 3.0Ghz Processor

or

Intel Core 2 Quad Q9300 2.50GHz.

Reason I want to know is because the computers I plan on buying has alot of the same features but this is on of the big differences between them.

What are you using it for?

I don't think there is any advantage to a quad if your programs will not utalize all four cores.

Using it for gaming. Also the one with the dual core one has 2 ati radeon 4850hd in crossfirex and the quad core has 2 9800 gtx in sli mode. So I just want to know which of these computers will be the best buy.

I'll go with the quad because of its processing speed

Very few games use a quad. The dual has a higher clock speed, so for games that use two or fewer cores, the dual will win. But I expect that the video cards will make more difference than the CPUs.

If you are using it for gaming, I'd go with the 2 core with faster clock speed. I don't believe that many games actually take advantage of all four cores.

As fishy said, graphics cards will make a bigger difference than processor.