Out of curiosity what kind of machine are you running on right now(CPU/GPU/RAM)?
If you still want your game to look pretty nice but also get better fps, DX9 frames is the way to go. However if you also want to use dx8 on an Nvidia GPU you're forced to rollback to like two year old drivers(Nvidia 306.97 found here) so your textures don't flicker.
EDIT: looks like I was a bit late sorry :[