I have a desire to learn more about "commercial" hot water heaters that have
the heat evenly distributed within the water, as opposed to just heating the
bottom like in a conventional hot water heater.

AO Smith makes the Cyclone and Vertex. A company called Phoenix (I think)
makes one that is stainless and therefore requires no anode rod (is that
true?).

Are there a bunch of companies that offer these products? Is there a
national wholesaler to turn to?

I'll go thru the Craigs Lists again, too. Just looking for a bargain.