Hi, what I do is bring along a really nice piece of material from a quality fabric shop, then I hold it up to the light next to a piece I like from JoAnn's. JoAnn's is usually much thinner with a fewer thread count. Also, I have found that the colors fade, a lot. I'm sure you can get nice material there, but when I'm putting in hours of work into something I want to be beautiful, I don't chance it with JoAnn's. I go with the name brands like, Hoffman, Moda, RJR, etc. You can't go wrong there.
Thanks, and remember, advice is worth what you pay for it!