If I go with the AMD, the CPU would be around 90 bucks and the motherboard would be 65 for a total of $155.
If I go with the Intel, the CPU would be 100 bucks (discount via friend) and the motherboard would be 95 for a total of $195.
If I go with the AMD, I could unlock the 3rd and 4th cores.
Is the I5 worth the extra money?
I'll be using the computer for Starcraft 2 and someday Diablo 3 at 1600x900 resolution. I don't really play any other games or really have a need for the PC other than just to play SC2 and D3 (someday).
Never bet on unlocking the extra cores, it is far from guaranteed. For only $40 more i would go for the i5 750, it will be quite a bit quicker than the 555 and is guarenteed to be a quad core, if you OC it it will beat out an OC'd 555 pretty easily in most tasks.