Hi Yvad,
A home lab for a VCP cert doesn't need a huge amount of grunt.
You wont need more then a single CPU.
Motherboard - Not to sure on this one.
If pricing is a big concern, have you thought about using the Hand on Labs instead of building a home lab?
Also if this is your first VCP, don't forget that you cannot sit the exam until you go to a VMware training course.