We are not looking at doing anything too major or spending too much as the games he plays mostly run OK, just some minor graphic problems and I think the money would be better spared to put to a better computer in a year or so.
He has already done a little bit of research and was looking to add 4GB (2GBx2), 240-pin DIMM, DDR3 PC3-10600 memory module.
And EVGA GTX 650 1GB GDDR5 DVI Mini HDMI PCI-E Graphics Card .
He hasn't got as far as researchng the PSU but if I've worked it out right, he'll need 600w +
Before I buy I just want to check we're on the right track with the graphics card? Can we do better for similar price?
You haven't really give a price range or specific vendor but I'll just say that a GTX 650 will be a somewhat decent improvement over the GT 440 of that desktop. It'd be more worthwhile to invest in at least a GTX 660 or AMD's 7870; both of which perform much better and are significantly more futureproof than the 650.
Are you saying that you're adding 4GB RAM/memory to the 4GB already present? If so, be careful as using two different memory modules models would most certainly cause problems.
As for a PSU, a 550W unit would suffice; you could up it to 650W if you think you'll ever upgrade again after this. Don't cheap out on whatever you choose, you wouldn't want any electrical problems. For brands that are trustworthy and reliable, Seasonic, Corsair (some of which, Seasonic manufactures for them), XFX, Antec, Enermax are highly regarded.
The memory is an additional 2 x 2GB to add to the 2 x 2GB already present. I think my son used the Crucial System Scanner and this was one "Guaranteed-compatible" options it came back with, so I was trusting them.