Totally amateur opinion here, but I think food is the answer too.
I cardio lifted 5 days a week (cardio+ plus high rep sets with weights), with a fairly strict 2000K a day diet, all the way down to about 184 and looked fairly buff, but wasn't very strong. I ditched cardio and went low rep 3-4 days a week for the most part and ate whatever I want within reason and am now 194, look much bigger but not buff, and am twice as strong.
I agree somewhat with Ryano. High rep with slow lifts builds slow twitch muscles to the max to gain size but not necessarily strength, but high rep with fast lifts like cleans or whatever will build fast twitch which grow bigger overall and will just torch fat off your body.
I remember reading that Alexyev ate like 7-8K per day, sometimes 24 eggs at a time, in order to keep up with his training (and then some obviously!
I think there's a tipping point between size and density too. I don't know what that is, but it seems you can get bigger, but not as dense (a low level BB'er for example), or get stronger and very dense muscles but not really much bigger (Naim Suleymanoglu for example).
Again just thinking out loud. Could be total crap. HA!