Whats best from a budget/performance point of view

Ok so i have been going through various reviews etc on the web all afternoon with various benchmarks etc, now I'm all
I'm looking to put a decent upgrade socket 775 CPU into my rig. I running an overclocked E4600 @3.0 at the minute and want to put a decent chip in that will last a couple of years until i feel the need for a complete upgrade to an i series set up, maybe sooner if they are really good.
The main use will be games and i have been initially looking at a Q8400. The thing is as far as gaming goes a E7400 performs as well or better in most of the benchmarks i have seen. Also the E8400 is the same price as the Q8400 and faster, so im looking for the best option, i dont want to get a slower Quad hoping that cores will matter in the next year or so only to find they dont and the dual core was the better option.
I cant find enough info that compares the differences between the various chips that I'm looking at. Obviously it needs to be a good step better than the 4600 i have now, which in itself is i agree a quite old chip. But i don't want to spend money for the sake of it either.
Its kinda the same thing as 64 bit computing. There isn't really any reason gaming wise to get a Quad (now) but there isn't really any reason not to either ??

Any help/Advice very welcome
Mactronix