Well in case anyone is interested. I put the gts450 fpb in today. With my old card, playing rift at the lowest possible quality setting (low quality renderer), I was getting about 60 fps. Setting the game to the highest setting of "ultra" got me down to 1 fps.
With the new card, I can run it at "ultra" and grab 40 fps. I had no crashes or lag and it ran smooth. I also used the pci-e connecter, i was calling it a 4 pin but its actually 6...so from this experience I am thinking the rails are cumalative, and that the pci-e utilizes this cumalative rail. If it doesn't I either got lucky or I'm playing with fire...literally, but so far I am happy!