For the case fans, you could get Corsair SP or AF series fans, but those have an annoying tone in the sound that they make. I made the mistake of getting some, and they ended up sitting in a closet for two years until one of my other fans broke. Even then, they were only in my computer long enough for the replacements to arrive.
The fans that come with the case are decent. If you want to upgrade them, there are much better options. Do you want to upgrade those, and if so, what price range are you looking at?
UPDATE: Sorry, that didn't answer your question. For case fans, you normally want models that are airflow optimized. It's worth mentioning that outside of a select few radiators, all computer fans will operate at nearly zero static pressure.