Good choice on not getting one, if ya really want on you can plan for getting one in the future. My 20" silver has been in several tanks as it has grown. The following tanks 55g, 75g, 120g, 150g, 85g, house the silver. it has always been in a tank at least 3x its length and and the width has always been greater then the aro length. Currently he is in a 180g. I am hoping to have a 375g like Shadowbass posted to be it's final home. He will live there with another silver and a black aro. Before that will happen though he'll spend a year or so in a 350 gallon (6' x 4' x 2') which I'm hoping to have going in a month or two.
The key to using the grow out method is knowing what tank you need and when you will need it by. It is also good if you are well established in your career and have a house.