Race Driver GRID
I tested this absolutely gorgeous-looking game with FRAPS, as well, and in order to keep things simple, I decided to capture frame rates over a single, longer session as I raced around the track. This approach has the advantage of letting me report second-by-second frame-rate results. I've left out some of the lower-end solutions here for reasons I'll explain below.
Yikes. So your first question probably is: what happened with the three-card 4870 X2 + 4870 setup? The answer: with only 512MB of memory per GPU, they just couldn't handle GRID at this resolution. That's why I've excluded some other configs, as well. They just can't do this. The cards with more than 512MB of memory can, though, and the 4780 X2 is tops among them.
Playing this gorgeous game on a four-way 4870 CrossFire rig at 100+ FPS on a 30" 2560x1600 display? Yeah, I love my job.