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.