i have found that buying a tool box is like building a garage, they always look big enough untill you start filling them. at home, i have 3 toolboxes [small] and various sections of peg board to hang tools. at work, i have two boxes that are good sized [like to keep very organized at work, and make sure stuff is locked up at the end of the day].
for home use, i vote for the biggest craftsmen box you can afford [not like you'll stop buying tools], and look for something that can be 'added on to', as far as cabinets, or 'center' sections.
this is my work combo, [pretty much filled to capacity