I seen a RZR at Stoney the other day that had a 35 quart (i think) Yeti and a Action Packer with a SWAG mount all mounted in the bed looked nice and clean
My rzr has a pelican dry storage box mounted in the back of it. Not sure how much they are because it was already on it when I bought the rzr but it works well. I strap on a tool bag on one side and a cooler on the other. I guess it depends on how much beer you want to haul. Here's a pic of mine.