I just upgraded from a Q6600 @ 3.2GHZ to a 3770k @ 4.3GHZ. Both systems with an HD7770 because I carried the card over to my new system.
Show me the picture where a Q6600 is compared to a modern i5 or i7. (just found one where the clock rate is 2.4ghz lol)
A Q6600 can hit 3.6ghz very easily and thats fast enough to get games to 60 fps with ease.
A Q6600 can not hit 3.6GHZ easily. It will do about 3.0 - 3.2 easily, after that you will need to be tweaking a lot of system voltages, ratios, timings, and other bios settings. Cooling also gets more difficult at that point.
There is a substantial difference in gaming between these two CPU's as well. With the Q6600 there was a lot of microstuttering that made games unplayable. Also, a frequent problem I was encountering, was that I would set the in game settings for a playable FPS when I first installed games (When there was no action) and as soon as the going got tough and there was a lot of action the FPS would drop to unplayable levels.
With my new i7 3770k @ 4.3GHZ. I can play games at frame rate I use to consider unplayable (24-35) and it's butter smooth!!! I have no problem playing single player games at 24FPS now, there is no microstuttering or lag! The Q6600 could play a game at 40-60FPS and not be this smooth. It felt like it was dropping frames all the time and stuff, just jerky and laggy even tho the frames were high. It didn't even really matter what graphics settings I used, it was always "shitty," no matter what the FPS was and I thought it was always my graphics cards fault. With the 3770k here, I now realize it was the Q6600's fault games played shittily.
You know how like, you would turn a corner real quick or enter a new area and there would be that split-second "freeze?" That little "freeze" that doesn't allow you to correctly position your crosshairs on an enemy so it gets you killed? It's a thing in the past now.