Computer Configuration

Hi Guys,

I'm Planning to buy a new computer and i m not too techie as far as computer hardware goes.

My plan is to buy a Quad Core Desktop. In doing my research i have come across so many configuration available just for Quad Core computers (of-course prices vary accordingly)

Softwares i use are Rhino 4.0, Grasshopper, Revit 2010. Could any-1 please suggest me:
1) Motherboard (AMD, Intel, etc)
2) CPU Speed in Ghz
3) Memory
4) Graphics Card
4) Miscellaneous or Other suggestions.

Thank you very much

Cheers !