Right now I have an HP Pavilion a6000n computer. I have around $350-$400 CAD to spend. I want to upgrade the motherboard and add another GeForce 8600 (the motherboard I have now only has one PCI-E slot). This will also need a new PSU because the one I have now is only 300W. Does anyone have any recommendations? My processor is an AMD Athlon x2 64 4200+ 2.2 GHz. For RAM, I have the 2x512 sticks that came with the computer which I don't plan to use because they are DDR2-533 (unless they're forwards compatible?) and 2x1 GB DDR2-800. It's also got a 250 GB SATA hard drive, an IDE DVD drive, and media card reader. Another thing, will the case be compatible?