Upgrade PC  

Hello, If I were yourself, I would be investing in a new motherboard and CPU.
They have new CPU's with multiple cores, like 2 in 1 sort of thing. AMD make a 6 core CPU.

Your wish list is a bit sketchy, how much RAM, what kind of video card, what kind of sound do you want.

Also keep in mind Mylot is the world, I don't know what country you live in, so I would suggest a squizzy at Ebay for price comparisons, and make sure that all your bits are compatible with each other, the vendors should be able to give you a list of what will work with what bits they have available.
I also suggest getting the bits from a local supplier for the ease of sorting out any warranty issues that may develop.

A purchase from an overseas seller will be much harder to follow up.