FSP makes a good PSU. DO you know what size 12V rails it has? the Amp rating? I think if you are leaving between $150-$200 just get a 8800GT and be done with it. Don't toy with the 9600GT or 3870. Just get the 8800GT it will last you longer. The EVGA mentioned above is an awesome deal, you should be able to easily OC it to 650 without any heat issues right out of the box. Or run stock, either way it's your best bet.
There was a 450W on newegg from FSP and was a 14A and 13A, not sure if it was yours. But does it have a 6 pin PCI-E connector? I think the requirements are 400W thought. You might be good to go.