Any reason why you're not getting a newer motherboard with CPU and RAM? And then you won't have to upgrade ever again, probably.
Actually The motherboard I'm using is newer than their original (Foxconn 661 MXPlus) and I am upgrading the CPU to a Pentium D so it should be enough to do what they want.
But mainly because their budget is kinda limited and they don't do anything incredibly taxing for a computer. They just want something that can browse the internet without a page taking an hour to load ( not kidding on this one ).