There's another new player on the market called the "Stealth" from http://www.undergroundcirculators.com from undergroundcirculators.com. The restaurant where I work got one recently and it's a pretty solid, no-frills unit. It has an impeller to circulate water and seems to heat 20 gallons without trouble. It has no features at all- you can't even switch the display from C to F. But for $500 it's a solid machine. Time will see how it holds up but it has a one year warranty. It's built & sold by a father/son team, the son lives near me.