Sa gaming ala masyado maitutulong ang CPU compared pag inupgrade mo GPU as it will only improve overall performance. That is kung galing ka sa cpu from ancient generation, probably better CPU will show improvement but not that much. How come?
I won't go into details but it should be obvious lalung-lalo na pag ni-claim sarili mo na techie :)
I remember I almost upgrade my q6600 P35 system to i7 860 but since I'm cheap and tight on budget it would be wiser for me to upgrade the GPU sell my current GPU instead. It turns out my system gained significantly faster gaming performance and I save almost 8k-10k. After more than a 1 year, I'm still happy!