I'm in Wildwood so, I don't really have a good LFS near me. The Petco in Ellisville is hit or miss. Aqua World in Ellisville doesn't have a great selects although their freshwater and pond livestock is great. Petco in Fenton is pretty good, a lot of selection, good prices and usually in good health.
I the closest true SW LFS to me are in O'Fallon/St. Charles area and South County. I rarely have time to travel that far just to visit a fish store. It's been over 2 years since I've been to any in O'Fallon/St. Charles.
And I went to SeaScape Studios a little while back, they are pretty good. About a year ago, I went to the Corner Reef and they were pretty good too.