Help finding a strong enough air pump

[eklikewhoa]

Looking for an air pump that would power 3-4 4" disc in a large tank that is about 3ft worth of water and 4ft worth of stand.

Been looking at some of the luft pumps like this one
http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3669+14684&pcatid=14684

or possibly this option
http://www.jehmco.com/html/diaphragm_air_pumps.html#DAPMH8-15


any advice or personal experience would be greatly appreciated.