for overclocking Intel cpus ( SB and IB ) an after market CPU cooler is a must
but IB cpus can get a lot hotter than SB cpus at same clock speed - the purpose of that article was to show how to keep the heat in check of IB K cpus with minimal possible voltage in Oced mode and have a look at the image :
IB cpus at 4.6 Ghz is roughly as fast a 4.8 Ghz SB cpu and the ~1.15v generates very less heat which can be kept under control with good after market coolers easily even in hot areas of the world like this but one can always experiment with muych higher speed provided he/she have a very good chip and adequete cooling equipments.