Have you guys ever looked at what they sell for commercial tank stands? Never seen a single piece of 2" material in any of them. My LFS had a 180-gal display tank made completely out of 1" stock. It's not brute force that holds the tank up, it's all in how you distribute the weight and transfer it to the floor. If you are going to have legs, you need a different design than if you are going to build a cabinet that contacts the floor around the entire perimeter. The other key is to triangulate enough with your fasteners, etc. to keep the thing from racking.
That's not true in many cases. As soon as you put shims to level the stand it bears only on those points.