The thing about "screwing graphics" because you want more units; I don't think it will help THAT much. Each soldier on the battlefield is controlled by the processor, so if you want as advanced fighting as possible (each man on in a regiment has a will of his own, etc.) you can choose either with 10.000 troops with a modern processor, OR a 100.000 troops with a 100 cored 15GHz processor.

I could be wrong though, but it seems logical IMO...