If you're going to use it mostly for gaming go for a nice Wolfdale dual core. Granted, the quad is easy to get to 3GHz but the Wolfdales are easy to get 3.5GHz+, and for gaming you don't need two cores.
Down the road when more apps need quads, the Q6600 is gonna be old and there'll be a lot more to choose from and cheaper prices.
In other words, I'd get an E8400 for example, overclock it and roll with it. That'd last you until the quads are the "big thing", then you can pick up whatever sweet quad that's popular then.