Most of my stash is made up of fabric bought on line that turned out to be not quite what I thought it would be. When I used to have a LQS nearby, I would take the top in to choose a backing. Now that I choose backings on line, what I do is put a photo of the top up on my monitor while I browse for backings, so that I can see them together. It works pretty well, but there's always a chance that a fabric will look different in person than it does on a website.