Graphics Card, RAM and Power Supply recommendations

[MultiplicityCM]

Hey guys, basically an old friend of mine built this current gaming PC for me a few years ago and we're no longer in contact so I don't really have much of a clue about it myself so I'm looking for help, I'll find a way to get it all together, I just need to know what parts go together, what I need and whatnot. I'm looking for a graphics card, power supply and some RAM (looking for 8GB) recommendation. So far I have a motherboard and a processor but I'm not sure if it all goes together so please forgive my stupidity Keep in mind I can't spend too much on it but I don't have a strict budget, best way to say it is I just want a rig that will run modern games well, doesn't have to be max settings for 2012 demanding releases just good enough to play anything on decent settings out at the moment. I'm not buying a monitor or anything like that but I may update my OS as I'm still running XP but I might wait a while as money isn't limitless for me. I don't need all the parts straight away, I just would like help compiling a definitive list to successfully upgrade my computer.

I'm thinking of getting the Asus M5A97 PRO motherboard and the AMD Phenom II X4 965 3.4 Ghz processor. Are these worth buying and is there anything else I've not listed that I'm forgetting that I may need? I'm only planning on upgrading not building an entirely new PC so I don't need a case and things like that...I don't think anyway

Any help is greatly appreciated.

 

[MultiplicityCM]

Anyone that can help?