Two suggestions for you to investigate
AMD systems using the Hexcore Phenoms in a motherboard with an 880G chipset [ onboard ]
This will be cheaper and perform as well or better than the intel system based on the i7 870
The second system to consider is an i7 9xxx series cpu , with a motherboard that can run triple channel memory . Im unsure if there are m-ATX boards that use triple channel , or whether they will boot without a graphics card . None have onboard .
Theres a charts section of this site where you can get a good idea of relative performance in apps