Most of what was said was true.
In gaming you'll often only being using 2 to 4 cores at most so the difference in their true gaming power can be quite large.
A decent way to test would be to run 3D Mark Vantage with MSI After Burner up showing your gpu usage as you go through the benchmarks, after it's over you can see how far your AMD chip is capable of pushing your gpus.
As a point of reference here are my two 470's which I believe should be slightly slower than your 6950's as well as usage for the entire second test.
3D Mark Vantage is dual threaded, however it isn't what I would consider a cpu intensive dual threaded test, you'll find real world games will result in less gpu usage even at 1080p than you'll see with the performance present in 3D Mark Vantage.
All that said Intel won't have anything coming down the pipeline that is going to beat out the i5-2500k in price vs performance. It's next products (Sandy Bridge x6 and x8 cpus) are going to be high end "expensive" parts, Ivy Bridge doesn't come out until 2012.
Edit: Also at your res you'd see even larger gains with a SB cpu, I however would upgrade to at least 1080 or higher (you should be doing very high res with ATI cards as 1080p and lower is where nvidia is better).Edited by BallaTheFeared - 3/27/11 at 9:03pm