Best bang-for-buck upgrade from 4850e & 9500GT?

[CuvisTheConqueror]

Hey, I'd like to get Dolphin running on my living room PC. Currently, I'm running an Athlon x2 4850e and a GeForce 9500GT, and in brief testing using Tatsunoko vs. Capcom, I get a noticeable pause when hits land, as well as bad framerates on some stages. Do you think I'd be better off spending money on a new CPU or a new GPU, and what would you recommend that's HTPC friendly (i.e. low-power, low-heat, low-noise)? I know both are pretty out of date, but of course, money's always an issue.