I got those surplus fans just now for $1 each brand new from this http://sfbay.craigslist.org/eby/sys/2195359595.html. Those guys are actually a prebuilt computer company that are getting rid of their stock oem fans from cases and cpu coolers. If you live in San Jose or Fremont, you should check that out.
I can't find the spec sheets on those Silverstone fans. The one on top looks similar to to their FN121 and runs pretty quiet. The dimpled 7 blade one I can't seem to find any info on it. Not sure what the dimpled blades do.
Edit: They also have 140mm surplus fans, but if you any specific fans in mind, you should bring it up cuz they will randomly grab a few and throw them at you if you don't.