If you decide to go AMD I would suggest the *Phenom II X3 730 BE. Only about 10$ more, but from what I can see well worth the few extra dollars. If you go Intel the E7400 will due very well. When combined with a GeForce 9800GTX+ (only set-up I have used the 7400 in) it can run AH on max (2-4K shadows) at 60FR easily.
Really it's a personal choice. AMD AM3 will hopefully last a while (since it's their newest) and LGA 775 is showing age, but still does very very well.
One thing though: RAM. You have 4GB (2x 2GB sticks) for DDR3, you want to run it in Triples (hence DDR'3'), so set-ups like 3GB/6GB/9GB (3x 1GB/3x 2GB/3x3GB...do they even make 3GB sticks?). Also, DDR3 isn't really needed for the price. The Phenom II's run perfectly on DDR2.
Just some ideas thrown out there, good luck.
