Truth be told the Plano 3600 may be the way to go for tournaments because you are bringing a deck already put together. As for keeping it secret, I would say put the 3600 in a sling bag or back pack type bag.
Cost wise the Plano 3600 is going to set you back...just about $3.00...LOL. I use the Plano 3700, one each for each color, gray, yellow, red, and blue (and one extra to hold the two base sets with instructions and tokens.). The 3600 is going to do the same thing just on a smaller scare which will hold your cards, dice, and tokens for your tournament. I also sleeve all my cards and use a hard case on top of being sleeved for any/all character/location cards. Both the 3600 and 3700 will have plenty of room for sleeved and hard case cards with the 3600 being a better option for just tournament play seeing as you use the same cards/dice all tournament.
What makes the 4700 great is that you don't need a separate box for different colors. Everything fits in it on one layer so you don't need to pick through dice to find the ones you need.