Thanks for the review PCM2, I was a great read and It's always good to read the opinions of people who actually own the hardware as well as professional review sites.
And you hit the nail on the head. Benchmarks aren't everything, they don't tell the whole story. I noticed the same when upgrading from my 4870x2 to the 6950, in benchmarks the 4870x2 would perfrom nearly as well, but in actual gameplay the 6950 is much faster.
To the people asking the OP to run his Q6600 at 3.6Ghz, well he has already stated that He tried to go higher and it won't. Not all CPU's overclock the same. I have a Q6600 that's supposed to be a great overclocker, but, no matter what I do it isn't stable beyond 3.1Ghz.
Also some people are mentioning the 1.1Ghz clock difference and saying that the scores aren't so good. Well the OP again did say that in actual gameplay the 2500k is way faster. But even looking at the scores I would say that the the 2500k is way better than the Q6600. For example, in the night fight benchmark at 6500m, you can say that there is only 8fps increase in min framerates and say that it's pretty poor. But, if you look at it another way the minimum framerate has more than doubled by using the 2500k. Doubling the frame rates is pretty good result in any benchmarks.
Then the 2500k uses way less power even with a massive overclock. It stays pretty cool as well. Which are other reasons you might want to consider upgrading from the Q6600. And if you read any of the reviews, you will see that in any application the 2500k is way faster than the Q6600.
And despite everything I said above, I am still on the fence about upgrading to sandy bridge. Because the Q6600 is a great CPU, it's starting to show it's age though.
PCM2, your review here has pushed me closer to the "buy" button. The min framerates are showing great improvement.
I've got the itch, but I must resist!!!! My Q6600 is still performing I must remind myself!
LOL, yeah me too, but every review and user opinion I read makes it harder and harder to resist.