I am just going to toss this out there, but that old Athlon is pretty slow by todays standards. Adding a new modern GPU is going to help some, but don't expect miracles from that processor at 2.2 ghz. I agree that for the price, that 450 would be a great value for this system, it will add better shaders, higher direct X capabilities, but performance wise that processor is going to rain on the parade a little I am afraid.
I have a 5570 and it performs well for such a small card.I play games like L4D,BF2,Starcraft2 and many other DX9 games almost maxed out but i also have a Phenom iix4.Still the 5570 packs a great punch in a small package.It has DX11 if you ever need it.
EDIT:What is your budget for the GPU? Maybe just getting a cheap Athalon ii x2 or x3 would make that computer last longer.
What socket is the mobo? Is 939 in anyway compatiable with AM2?
Was looking at the prosseseros and the budget could be possible for both but i need to know the socket type.$50 for the prossesor and $70=$60 for the Gpu.With a new prossesor it could extend the life of it for another 2years depending on the PSU and how old that is.
Yes, x1 of each would be way better than a 7800gt sli
Well i still stand by my reccomendation for the 5670.
That is a great board otherwise i would say to get a newer cheap one with only a single slot x16 so you could get one of the newer chips.I would say not to buy the FX60 if it's only going to give you 400mhz more,when you can probably obatin that through an O.C., although they are cheap.