it could, if the program you are running is not made for quad cores, it will perform like a e5200 and mostlikely bottleneck you some.
have you tried to overclock any?
Nope and i do not know how..
Btw is there any game using quad core yet?
Supreme Commander forged alliance comes to mind. A few others as well.
CPU bottleneck is obvious in some Valve games on the source engine. Valve recently released an option in settings though so you can take advantage of more cores. This was for TF2 and L4D and showed some great performance results. I'd go for a PhII tri core/quad btw rather then a q8300. You probably will get better performance and wont be on a doomed socket.