I agree. Not my project though.
By my rough calculations, sandybridge igpu should comfortably beat the 6800 which is "the last 9x" gpu without workarounds, basically bugs/missing features aside, implying great performance in all 9x only titles (not xp+). 9x only titles should have broadly stopped by 2002 after xp. Very few devs would have not known xp was coming by 2001, and mindlessly continued down the 9x path, so it may have been earlier. I'd actually assume by 2000 they would have known which apis are likely to be deprecated.
In any case, sandyb should be more than adequate.
Scale your expectations accordingly.