The 9400 GT is a very low-end card. You won't get that much of a performance boost. There are alternatives that use equal or lesser power and still deliver better performance. So, I suggest you get a new card.
Thanks everyone, I just had it sitting around, and i tried putting it in and it ran for a short while, but then crashed while playing planetside 2 beta...doesn't crash when I use integrated graphics. Well, time to start saving