I have Q6600 too. I am actually happy with my processor when it comes to gaming as it works with almost any game as long the rest of the system is decent ,but unfortunately I had some issues with my old motherboard and rams. so I decided to buy a new system instead of upgrading since it's difficult to find working DDR2 motherboards and rams. I would say Q6600 is worth, but it might increase the electricity bill. if you can't afford for a new processor then stick to Q6600 unless go for a new processor. if you decided to overclocked Q6600 then it will increase the electricity bill even further so it's not worth at end of the year. 5820K looks like a nice CPU ,but do you think you can spend for a 140 W processor?