I suggest you use Google and decide from the recommendations.
Ive had a brief converstaion recently regarding the AMD Phenom 9600 Quad core,and apparently its a mean piece of kit...very powerful and absolutely flies.
I believe sometime in April the Intel cpu's are due to come down in price...maybe worth the little wait.
Any of the above will serve you just fine....but even though im an Intel fan i could be tempted by the AMD Phenom 9600 Quad core.
Just make sure you get a good mobo,and this may need a bios update to handle the more powerful cpu's.