I also tried Call of duty 2 with 1.3 patch, but single core is able to handle it with 85+ fps most of the time. During heavy firefight in later missions it can drop to about 50-60 fps which is still manageable. Graphics details on maximum. This is probably where you would benefit from dual core.

In Company of Heroes I have found it impossible to defend territory with just infantry and vehicles even on easy difficulty as AI attacks multiple sectors simultaneously. Any tank left unattended will get destroyed by AI AT gun. It's probably better to build machine gun nests and AT guns. Still, AI is very good at finding weak spots. The problem is mainly in 2 player maps as the front is wide. This is an issue in skirmish games. In campaign it is manageable as AI is easier. It will not swarm you with tanks.