Best place to buy plumbing fixtures?

[Laurie Clarkston]

I am turning an empty building into a four plex.  I need to buy all the plumbing fixtures and sinks.  I had previously been told by a contractor that Lowe's and Home Depot don't have the same quality fixtures as plumbing stores.  Is this true?   What's the best place to buy these?  Big Box, local hardware, plumbing supply?  I am located near Springfield, MO if anyone has specific local suggestions.