TBH, the OP needs a complete new rig.
Once the PSU and GFX are replaced then the CPU, RAM and MOBO are gonna be the next issues.
Could go for a Intel i5 2500K CPU, very mucho bang for dinero
Mobo to suit and about 8GB of RAM.
and while your there, might aswell invest in a SSD or two for super speedy load times
Does he really need to go for SSD???
What you are asking him to do is rebuild his PC. Looking at his first post, I take it that his technical skills with a PC are basic.
SO... IMO, I think he could get away with a pre built base unit from somewhere. Check out places like Currys, Comet, PC World etc. Look for their discontinued stuff. It'll be maximum 6 months out of date, but reduced to match. Yeah you won't be able to play the games at it's best, but it'll be pretty damn good. Unless you wanna give me about £5-10K+ to build you something amazing and OTT for your needs!
I was hoping the OP would realise that a new PC is in order, self built or ready built. Choice is his
£5-10K???? What you building it out of? I only spent just over £1K on mine total. I love my 16GB of RAM