With the S1 and 1 x 120mm fan it will keep it cool enough also use mx2 or artic silver 5, now if you don't have that cooler the stock fan is fine, but you need to flash the bios with a better slope and percentage for the fan speed or do another profile is another option and increase fan speed that way.

So the stock fan is OK, but not OK at stock or Overclocking speeds unless it is Increased one of the ways i just stated or yes aftermarket cooler and fan S1 with a decent 120mm fan and with ramsinks will do the job too.