According to the guy who loves giving away 8800GTX cards to a complete stranger, you can use a 7600GS as a dedicated physics card with the upcoming 680i/680a chipsets.
From x-bitlabs
Q: Why are there two power connectors in the 8800GTX?
A: This is done for the future, for scalability. As soon as motherboards are equipped with 4, 8 or more PCI-E slots, this solution will become a necessity. How can we use three slots now? Two cards in SLI mode, the third card, for example the 7600GS, for physics.
http://www.digit-life.com/articles2/video/g80-part4.html
From x-bitlabs
Q: Why are there two power connectors in the 8800GTX?
A: This is done for the future, for scalability. As soon as motherboards are equipped with 4, 8 or more PCI-E slots, this solution will become a necessity. How can we use three slots now? Two cards in SLI mode, the third card, for example the 7600GS, for physics.
http://www.digit-life.com/articles2/video/g80-part4.html