how loud is the intel stock cooler on an i5 4570?
It's loud. Not as loud as the ACX cooler on my GTX 760, but loud. I just picked up one of these http://www.tomshardware.com/reviews/low-profile-heat-sink-mini-itx,3639-17.html and plugged it in to the second CPU fan jack and put it right up against my head, the stock fan was the length of the cnps' cord and I could hear the stock cooler more.
It's inaudible under a table when it's idling, web browsing etc. but if you're doing anything intensive / anything that'll get it hot, it gets pretty damn loud.