Personally I don't think Q9xxx to i7 is worth it. Anything within one or two generations is not that big of a deal as long as you have high enough Mhz. I am running my Q9450 easily at 3.4 all day long and most of the time my 4 cores are just resting.
As for you gamers, you will benefit far greater from a new GPU than a new CPU. Trust me.
As for you gamers, you will benefit far greater from a new GPU than a new CPU. Trust me.