well for that kind of money you can buy a stick of 512mb ram and make your memory total 1 gigabyte. but there's no way you can do better than the fx5200. you simply don't have enough money.
there are 3 main interfaces for video cards:
your computer is a bit old, so it most likely will not have a pci-express slot. you can run cpu-z (google it) and it should tell you what your video card interface is. its not clear whether you have agp or pci. if you have pci, there's really not much else you can do. if you have agp, you have a few options, but definitely outside your price range.. a good starting point for good cards is this:
when it comes to video cards, its not all about memory.. the cards have different cores, with different number of pipe lines and pixel shaders, etc etc; so it gets a bit complicated, a card with 128mb can outperform one with 512mb (..rare..). price isn't always an indication of performance. even the memory itself can differ, there's DDR, DDR2, AND DDR3 (and soon, DDR4). only way ppl know whats better is by testing them out and looking at benchmarks.. specfications can only tell us so much.
found another card with similar performance/price...