I can't choose my next CPU, so I need some help here

I want a good CPU for gaming and benchmarking. Everyone says that the Dual Core are the best for gaming, but the quad are the best in 3dMark 06.

So my last choices are these three:

E8400 - about 180-190€ new
Q9450 - about 290€ new
Q6600 - about 225€ new - 180€ or less used

Wich one is the best option at this moment? I don't know what I would do in future, so it can last one year or more, or just some months.

The E8400 is cheap (new), is 45nm, 3.0GHz stock and I think it can get to 4Ghz easily.
Then we got the quad. The Q9450 is newer and more expensive, and I don't know if there is much difference from Q6600, apart from the lower vcore and maybe a bit colder?!

Need some advise here...

I just want a good CPU for gaming and benchmarking, maybe with a new 9800GTX.

Thank you all!