8400 will goto 4ghz with the stock cooler and with 1 minute of bios changes. Why wouldn't you overclock?
Thats not true for every E8400, nor would I say the majority.
Games like FSX, Empire: Total War, Dawn of War 2 and Supreme Commander. Are taking advantage of multicore CPUs now given their nature (simulation/RTS). These games clearly favor a 720BE over and E8400.