I second the idea of using a G3258 for an HTPC or dedicated dolphin/emulation machine. I know more about AMD gpus, so something like a 7770 or 7850 (practically the same as a 260x or 270x) should be enough. The gpus can be found for <$100 on ebay (or sometimes newegg runs a sale for about that price, too).
A system like that would also perform OK on PC games, though would be CPU limited in some that are pretty multithreaded.
A system like that would also perform OK on PC games, though would be CPU limited in some that are pretty multithreaded.