Stay away from the 45.xx drivers. There are numerous bugs in those drivers and they can leave DX is a rather bizarre state as it pertains to changing your video card.
If you want stability with DX9, use the 30.82 or 41.09 drivers.
Omega's drivers are nothing more than registry tweaks. Not saying that is a bad thing, but NVidia has been leaning on Omega to drop the drivers.