See, if it was a question between E8400 and Q6600, my answer would have been different. But E8500, you say ? Forget about the rest. Even if you are concerned about future, all you'll need after 2-4 years is an expenditure of around 2,000rs more for a good aftermarket cooler and there you are doing 5.0Ghz+ on your E8500, crunching numbers like worms....
But then again also remember that to overclock your CPU to the level I have mentioned you'll need either:
P5K-V (~9,000rs)
P5Q (~11,000rs)
P35 Neo-3 (~8,000rs)
Motherboards..
hope it helps.