CPU Question: I have an overclocked e5200(i can still overclock it more) but i can buy e6600 core 2 duo also..?

should i buy it or just leave my e5200 pentium dual core in for now? I am still able to play games like Duke Nukem Forever, Bad Company 2, Starcraft II, etc after an overclock from 2.5ghz to 2.9ghz and an fsb of 900mhz up from 700mhz. is it worth the upgrade or not? thanks in advance.