Yep. GP4 is the thing. Better looking and with a far better AI than any ISI / gmotor game that ever came out. And the driving physics are simply in a class of its own.
Once upon a time I was even a staff member at grandprixgames.org. The sad thing is that GP4 isn't as easily modanble as the gmotor games. Else I'd never turned my back on GP4 !