I am going to assume Q6700 is a mistype for Q6600, as that is the only 65nm quad that makes sense.
For gaming it will depend on whether or not the game is multi-threaded and if it supports more than 2 cores. If it doesn't than the one with the higher clock speed will win out (although Q6600 has more L2 Cache iirc). If you are factoring in OCing the E8500 will probably be able to go farther than the Q6600 will, due to requiring less power and producing less heat. If you are talking about games right now the E8500 should win out, although it won't be by much since they are both competent and the GPU effects fps more.
That said I would still go with the Q6600 as it will proved more future compatibility. Better yet, save for Core i7, chances are it will blow all of this away.