All the new games are going to see an increase in Dual Core, Oblivion already does see quite an increase when you run Dual Core.
And yea unless your on a tight budget, the C2D are quite a bit better after overclock. Stock for the money they are very close but still the C2D is better at most things.
E6300 w/ Arctic Freezer Pro 7 @ 3.6ghz 1.4Vcore
Antec 900 Case
EVGA 750i FTW Mobo
4x1GB of G.skill DDR2-800
2 8800GT in SLI
22" Samsung Syncmaster
1 250GB WD and 1 Seagate 7200.10 in RAID 0
Corsair 520HX 3DMark06 Score: 13900