I see a lot of people go with these
http://www.walmart.com/ip/Coleman-Xt...Green/21947771 it's 150qt and has guides built in so you can add your own shelves. Standing the cool up it is more like a fridge, you can either use wooden shelves, or many people buy the white wire closet shelving and cut those down, I remember reading that one 4' piece of shelving cut in 3 equal pieces fits perfectly.
It's 70 bucks on the site but I think it's cheaper in your cart, around 60 and free shipping (at times*).
Happy smoking!