Cores in gaming are normally like a 5th wheel on a car.
I would say this however, when testing Crysis 2, I noticed an E8400 (overclocked heavily), showed both cores at 100% for practically all the playing time. Not exactly a slouch of a cpu.
I'd get confirmation off someone who's played the off-the-shelf version, as there are often test routines running in beta apps and of course some finishing off to do.
May be an anomally, and if you don't care about the 1 game and/or you're not bothered about playing a game whilst something akin to orthos is running, it may be irrelevant.
(A Q9650 it leveled out core use sensibly)