The most power fool air pump i ever had (still have) is the "Pump"
Made in Japan cost new about 200$(well that is few years back maby cheaper now). You can have twelve air stones running on this one.
I think there are few models. Mine is # 10.
http://www.hagen.com/usa/aquatic/manuals/thepump01.cfm
This is how it looks like (mine is first one in line)