Ah right cool, well seeing as you're moving from a mighty Q6600 I'd go for a Phenom II 955 X4 Black Edition.
3GHz and fairly overclockable, don't worry about the 8Mb of cache being low, it's used differently than on intel chips.
Then there's the 965, same chip, just 3.4GHz, oh, and I'd recommend a good 790FX board if you want to clock it.
They perform on a par with Intel equivalents for less money, unless you're looking at media editing, where Intel has the edge.