GPU doesn't help for CPU-intensive tasks, though, so the performance advantage there is moot. Even if Snow Leopard does contain something that makes massive use of the GPU, Apple would still have a tough sell convincing people that the new Mini was faster than the old one... people are quick to recognize that 1.83 > 1.6... it's a lot tougher to explain that 1.6 + 9400M > 1.83 + X3100.
I don't know - I still have this feeling that Intel will give Apple an updated version of the Atom that is a dual 1.83.