fj123 wrote: I can't speak to their mustard selection, though.
Sunset foods in Highland Park, Northbrook, etc has a large selection of mustards and other condiments. The great thing about Sunset is that they will order and stock any product (in my experience) that you ask them to carry. So if there is a particular mustard you seek, they either have it or will get it.
I also second the recos for the delis at for The Roumanian, Kaufmanns and Tel-Aviv. They are all regular stops for me too.