Also what you want to look at is the Litres Per Minute not necessarily the gallons per hour, you want to know how much actual air you are pumping in and with a 700 gallon that is about 45 LPM so if you hooked up that along with your current one which may be putting out 15 or lets say 20 then you are around 60 which is waaaaaay better than where you are, however if you want trees man I suggest you go ahead(of course if it is financially feasible) and get the one in the link above or similar to it. But at any rate I would get the highest LPM pump you can afford
I promise you will go nuts as soon as you plug that bad boy in and then you will get to literally watch your plants grow overnight!!!! That is how I was able to see my last ones grow sometimes a couple inches a day
I am really glad that you are going to get one soon because you will be so happy that you did. Again I promise this is the best advice I ever received from a great experienced grower who once told me "Cannabis plants love, almost above all else, lots of air to their roots" this is the reason why I choose to grow in DWC because it is the most effective way to get o2 to the rootzone. You are doing such a good job at this point I want to see you take it to the MAX.
Happy grow and air pump Karma coming your way my friend!!