Well I got the cheaper version of the Auralex isolation pads, and you can tell the quality is just a tick off. Actually I don't know if I'd call it quality, just a different texture to the feel of the foam, but it gets the job done just the same really.
Now I'll say something controversial. I will swear that it makes a difference in sound quality. Is it like the end of the world you don't use them or is it something I can measure, no I can't, but to me it makes the speakers more airy, like they are floating or something. I know sounds strange, but I think it makes a difference, and I'm glad I got them. Now my front mains, a center channel have them under them. I'm happy with it. Just my opinion.