Mate, I know you want to play this game smoothly - but your Power Supply really is the biggest limiting factor.
Whilst the 430 may be fine according to some, It's still a 300W+ recommendation card.
Bluntly put - you won't find a 220W compatible card that will run FO3 smoothly. That PC is simply not designed to be a gaming machine.
You may get away with using some of these cards for a while, but in the long term the PSU will be pushed to it's absolute limits and will fail eventually.
Under a 'heavy load' , Realistically you'd start facing sudden shut downs as the PSU degrades with increasing intensity until after one shut down too many - the PC will simply not turn back on. That also risks the other components that might get damaged when the PSU finally fails completely.
Low profile cards are primarily intended for HTPC use with some occasional 'light gaming'. One common factor is that they also require a PSU with more amperage/wattage. Your current PSU has neither.
Honestly - a cheaper way of playing FO3 would be to buy a 360.