Depending on the game, running the 955 @ 4.0 GHz will either completely remove the bottleneck or at least remove it quite a bit. In some games though, the i7 will still win, however that is to be expected. Others, the Phenom will beat the i7.
If you're talking about benchmarks then yea you will see some bottleneck. But in actual gaming, just crank up the graphics and it shouldn't be much problem. You may see slightly lower minimum FPS than with an i7 but it shouldn't be too bad. OC would help for sure.
For example, I have an i5 750 with CF 5850s. In Vantage I score a higher GPU score but lower CPU score at 3.68ghz with turbo on for up to 4.2ghz 1/2 cores compared to a straight 4ghz OC. It's pretty wierd but I guess the GPU isn't multi threading very well. While gaming tho the FPS is very good and I'm not sure if it's better with the turbo OC or the straight 4ghz... hard to say, but either way the GPU usage is usually 90-99% only sometimes dropping a bit briefly to 80% or so, and I believe that coincides with a slight CPU bottleneck at specific high CPU demand parts as the FPS drops along with it.
Anyway, even if it's a slight bottleneck the FPS should still be very good.