i think throwin in another 8800gt would be your best bet:)
jealousy >: (
try to get another 8800gt that is equivalent to your current 8800gt though becuase the system will automaticly choose the lowest clocked card as the default speed for both cards.
and oh yeh, setting up multicard configs is a pain in the butt as far as installing drivers goes.
had "tons" of fun trying to get my 3870s in crossfire