Pretty much what Mondoman said. The nice thing witht he 45nm is the fact they run cooler and use less power, which makes it nice for overclockers. But in Stock performance you won't notice that big of a change except in synthetic benchmarks.
After 3.6 Ghz I never saw any improvement with my old E8600, and I could stably hit 5.1 Ghz on water but it didn't boost any performance. My old, old E6750 was easy to set to 3.6 so an E6850 should do well.
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