There is no way that is possible. The 2600 isn't even in the same class as the 8800. Its designed as a replacement/competitor to the 7300 and an 8600 in pc. The 8800 even beats the 1900 by like 80%. Unless there is a HUGE driver issue with the 8800 or pro aps are ridiculously lopsided then its not possible.
yea the driver isnt utilized as well as the hd 2600, just wait until 10.5.3 or another graphics driver update.