both are 256mb but i want your opion on which one to put in my old backup rig.i own both of these cards as well as a nvidia 6600gt
If you are not gaming with it use the 1650 pro it uses less power and can be used with a weaker psu. The 6800gs will have the edge due to bandwidth over the 1650 pro (I personally own a 6800gt) but has a much lower clocked core. 430 vs 600 mhz at stock clocks. I would use the x1650 pro hands down even if the filrates weren't that great.