I do store quite a lot of my posters in a plan chest. It's an A0 size so it will fit quads in with no problem. I only store clean posters in it though, as I am concerned about contamination from things like tape or marks that might transfer, so any posters that have any thing like that on I store seperatly.
The plan chests are quite large, but very sturdy. They do swallow up a vast amount of posters, and you have a large surface on the top if you need to lay anything out. I picked mine up for £60 in the U.K. from Ebay, I am sure there must be something like these in the U.S. just be patiant though, and you will get one at a reasonable price, as they can go for quite a bit of money.