I agree with Chris.
Never limit yourself to just one box. It would be silly to just try and squeeze whatever your equipment you deem to be necessary just because it fit into that one tin.
More means more choices. In an emergency situation, why limit your choices ?
We all carry what we deem necessary and if it goes beyond the standard PSK so be it. As long as you are comfortable carrying it.

Of course you may want to limit how much to carry, or else you'll end up like Crazy Eric <img src="images/graemlins/blush.gif" alt="" />