I think you are making some confusion. Dual is one thing and FSB/RAM ratio is another thing. It's good that your ram is syncron with CPU (FSB) but that means your ram is running at 667 mhz.
If you change the ratio just for the ram to run at 800 mhz, the system will properly run poorly. I recommend to keep it as it is (FSB/ram 1:1).
If you want to run dual channel, you should buy one more 1 gb.