Yes about PSU it's necessary to change it so what about - Fortron GHN 460 W??
about cPU - yes I will upgrade it in a few months but my Motherboard is also limited to X2 and X3 phenom - http://www.gigabyte.pl/products/mb/specs/ga-m56s-s3_1x.html
Btw. will there be a lot difference between PCIe 1x16 and 2.0 in GPU?