You can stick with the intel stock cooler, but I wouldn't recommend it. (Loud, hot, nasty)
CM Hyper 212 evo or Zalman CNPSX10 PERFORMA is good.
Or if you want to go up a step, Corsair H55 is a good AIO watercooler.
I use the CNPSX10, chunky, restricts RAM height, but it's good at what it does (was cheap too).
I also have a H55, very quiet, keeps my GPU nice and cool. (OC'd 780, got a conversion bracket)
You could run 4GHz quite happily on the stock cooler, but I'd expect 70-80C.
Not great, but workable.