How big of an air pump

I am making a 6 bucket recirculating DWC system. I am using Active Air 4 inch disc air stones.What would be a good
air pump for these stones. After considerable research, I am leaning towards a Pondmaster model 40. Would this be a good pump or does anyone know of a better one?

here man

http://www.amazon.com/Hydrofarm-AAPA15L-6-Watt-15-LPM-Outlets/dp/B002JPEVMC/ref=sr_1_10?ie=UTF8&qid=1378691870&sr=8-10&keywords=air+pump
http://www.amazon.com/Aquarium-Airline-Tubing-Connectors-Filters/dp/B0051SM6GW/ref=pd_sim_lg_14

this is a very high output ............u can take 4 short tubes all same lenght then add a t fitting on 2 to make 2 sets then anouther short line with anouther t fitting gives u 1 line with all the power

http://www.amazon.com/Deep-Water-Innovations-Micro-Pore-Diffuser/dp/B004OYDB40/ref=sr_1_1?ie=UTF8&qid=1378692163&sr=8-1&keywords=micro+air+diffuser

that stone there makes very small bubbles and will make the roots very very happy
[video=youtube;9H45lTR5I_8]https://www.youtube.com/watch?v=9H45lTR5I_8[/video]

for DWC u want to look for something like this