Originally Posted by VulgarDisplay
I think that processor is a bigger issue than your GPU.
Yup. For smooth playback without the vagaries of GPU acceleration, the OP needs to upgrade the CPU. May as well look into a completely new platform. Something like an AMD Trinity would be great for playback, plus have better gaming abilities than the 9400 GT. Not that it would be that great for gaming depending on the games played. Depending on what games the OP expects to play
, consider a dual core Intel (Pentium G2120 would be great) with a discrete graphics card such as the Radeon 7750 or higher.