DWC air pump

so i keep reading all these things about using .5 to 1 watt air pump to 1 gal of water. but this doesnt seem to make sense to me. wont the efficiency of the air pump vary by manufacturer? can anyone tell me how many gal/h or lpm pumps i should look for.
i need air for four rubbermaid totes with about 15gal in each one. i currently have two of tetra whisper air pumps rated for 30-60 fish tanks. i have used the two of them together quite successfully in one 15 gallon tote, but it is not cutting it with 2 totes at 15gal each. i plan to integrate 2 more totes to a total 4 and need a larger pump with which i can run the two tetra's for redundancy. another of my largest concerns is noise. so i dont really want anything bigger than i need. i was thinking about the GH pump because it looks smaller and quieter but i know i can find more powerful pumps for cheaper. are the bigger ones louder? thanks .http://cgi.ebay.com/GENERAL-HYDROPONICS-DUAL-DIAPHRAGM-AIR-PUMP-AQUARIUM-/360268363068?pt=LH_DefaultDomain_0&hash=item53e1aaf53c

for instance this pump seems to be quite powerful but only 8 watts..http://cgi.ebay.com/Rena-Air-400-Air-Pump-702E-/320635806547?pt=LH_DefaultDomain_0&hash=item4aa7622353

4 of those would work or one of these

http://www.horticulturesource.com/product_info.php?products_id=929

http://cgi.ebay.com/New-General-Hydroponics-Dual-Diaphragm-Air-Pump-Aqua-/290514191008?pt=LH_DefaultDomain_0&hash=item43a3fec2a0

http://cgi.ebay.com/Active-Air-Commercial-Air-Pump-6-outlets-Aquarium-Hydro-/290468543921?pt=LH_DefaultDomain_0&hash=item43a1463db1

I ran 18 gallon rubbermaids 10 gallons of water each with a 11$ walmart dual outlet pumps worked great and they tell you how many gallons they can push into

http://reviews.walmart.com/1336/10532634/aqua-culture-20-60-gallon-double-outlet-aquarium-air-pump-1-ct-reviews/reviews.htm

I don't think there's a huge difference between manufacturers. The technology of pumping air with a diagphram is well known and when you consider all the various ways pumps are rated the watts roughly correspond. Of the 3 pumps referenced above I could only find the watts on 2.

1. 8 watts rated at 1331 lph. Divide by 60 we get 22 lpm.

2. A 20 watter rated at 45 lpm is slightly more than twice as much air at 2.5 times the power.

3. is rated at 20 lpm and I'll bet it uses roughly 8 watts.

It would seem there's some fall off in efficiency at larger watt ratings, but that's pretty much normal. Size has consequences.