I like my Million Air 600. It is the quietest air pump I've owned. It powers a long bubble wall at the bottom of my 100g no problem with one outlet and 2 sponge filters in a fry tank with the other outlet.
I got one about a week ago. Best $10 I've ever spent. It has dual air outlets - I have them adapted to one hose, with a check-valve, and a pressure control regulator, all connected to one 4 foot bubble wall in my 150gal.
I have the regulator slow the air because it's UBER powerful. It can instantly fill my tank with millions of tiny bubbles - but my filters were sucking in too much oxygen so I had to cut it waaay back. I'd say this pump provides more than enough oxygen for any fish or plant in up to a 300 gal aquarium.