If this game is the most intensive thing you plan to do with the system, then a Dual core will be just fine. If you plan on using it for video editing, etc. then a quad core will be better.
With all things being equal, Aces High will perform better with a faster dual core as compared to a slower Quad Core.. but this doesn't take into consideration other things you plan to use the computer for.
If my choices for the same price were say a 3.4Ghz Dual Core vs. a 2.4Ghz Quad core, I'd probably choose the Dual Core, but if the speed difference or cost difference were more minute, I may opt for the quad core.
Example.. a 3.4 Quad only $20 more than a 3.4 Dual.. I'd probably go Quad.