Buy the biggest roll cab you can afford now. Down the road, buy a top box. When those two are full, buy a middle box.
If you are particular about organization, you well fill a tool chest up in no time with dividers, wrench racks, socket holders, and trays. Of course it is easier to find tools and you can look in a drawer and notice if any thing is missing. On the down side, space fills up fast. If you just dump things in drawers, they won't "fill" up as fast, but you'll waste alot of time digging through piles of tools to find the one you need.