Nothing crazy about it at all Rally. We do it all the time...Each hydro5 has the capacity to handle a 125 gallon tank...one in each corner...or if you want to go nuts...stack pairs...and a nice HO dual outlet air pump and you could filter a 110 for well under $50.00 let alone $120.00
What are you using for filtration in your current tank? I'd migrate that over and then add extra. Do not run a new tank with fish if you don't already have enough established biological filtration for the new tank!