I have the three Chess sets, no complaints from me on the sound. And I like his later Chess material fine. Also have a few of the Mercury CD's, the re-recorded greatest hits (which I actually like despite its reputation, but it has no real purpose at this late date), the Fillmore set, which can be had very cheaply online and you get what you pay for (lazy sloppy blues and the ghastly "My Ding-a-ling"), and "Concerto in B Goode" (love the side long instrumental title cut, not much to recommend the other side). I've heard the other Mercury's, and they're a mess. I also have the original 3-CD Chess box, which I'd like to find a good home for eventually.