Same here, regarding the Atlas and Fiction House books, and also Archie, DC, EC, and Dell. A lot of Hillman books reside together, too. It sounds like a lot of publishers broken out, but not when you consider the number of publishers in the 50's especially. And as far as the Dell boxes go, I have plenty of those as well. For one, they're so affordable, and a box with say Bugs or Donald in it is bound to have a dozen or more Dell Giants and those things take up a LOT of room in the boxes. So worth it, though, as great examples of Americana!!
(Oh, and then there is that nasty complication of some books being in mylar and residing in magazine boxes while the poly-bagged (egads, I know!) books can still fit in a massaged short box.)