you don't need a commercial air pump with that little of a set up. go to a pet store and get a air pump there, they are used for aquariums and they are very quite and will work perfectly for what you need.
Yeah, you don't need that. I run 12 Large air stones with my commercial pump. Aerating 30 gallons. I use the pet store ones in veg. Just get a larger aquarium pump.
im using a 60 gal one that came with my set up and a 4 gallon tote with 2 gallons of water and a 4" air stone. mine didnt put out too much at first but it will put out more as the stone soaks a while. also try putting it on a computer mouse pad or 2 to quiet em down if you go with the bigger set up next time! got a huge girl with the one air stone and pump at only 1 tsp per gal of flora nova bloom and well into flower and its working great. i just have a back up i use and lightly boil em out every other change to clear em of nute build up in the stones and works like a charm!