Something to keep in mind, the shape of your softbox dictates what you're trying to mimic in nature. Square/Rectangle boxes mirror a window with the sun coming in (I've even seen someone gaffers tape a grid onto the front of one). Octa's and beauty dishes are round and more sun like.
Strip boxes I don't have a relative light source off hand. Big softboxes are fun because with some foam core, you can turn a 4x6 into 2 1x4's with 4' between them.