Lets get one thing straight, there are many happy Mesh customers out there - its just that sometimes they go wrong and appears it is difficult to deal with their customer services at times - hopefully yours will be OK.
Regarding the C2Quad - no don't think of it that way, think of it as 4 separate cores at 2.4GHz which makes it better for multi-tasking - it doesn't help so much in gaming to be honest.
What I'm saying is you can't compare the 2.4GHz here with that of the old P4 - completely different kettle of fish.
Don't worry, You will be fine with the Q6600