This should give a pretty good idea on what to expect (NOTE: it is by no means a fully optimized score, no PCIe clocking, no OS tweaking etc):

watercooled 2900XT CF w/ 2 CPU cores vs. LN2 cooled 8800GTX SLI (older drivers) w/ 4 CPU cores (and slight CPU clock advantage for the nV rig also - 4876 vs 4804MHz):


Means that 4 cores running at 4.8GHz (CPU Score of 7000+) with watercooled 2900XT CF gives you 24k already