I have the case from my old PC and a beefy PSU. Can these CPUs take a lot of over clocking?

HelloYou have the case and power supply so why even look at buying an off the shelf PC?. you would even be buying the same GTX 250 graphics card all over againMakes no sense at all.All you need is a processor , MB and Ram, if you are not sure on what CPU works with what MB just buy a bundle from Overclockers.uk or even Novatech.Your E8500 will do 4 ghz without breaking sweat and will run FSX ok, why not just overclock your existing CPU?.You are asking if these i5-i7 CPU's are good overclockers but you haven't even tried overclocking the E8500 up to its full potential yet.

I agree with mad dog the most cost effective thing for you to do first would be to overclock what you already haveIf you want an increase in performance then your going to have to look at i7 920 or i7 930 cpu use a BIG cooler and something like an Asus X58 motherboard with some high speed ram and overclock up to or slightly over 4 ghz..If you want a significant increase in performance and have a big budget look at i7 980X with a GTX480 graphics card that will give you good fps and a smooth flightCheersSteve