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.
New player in the immersion circulator market- $500!
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Hmmm...it has one odd quirk. You're supposed to set the display one degree above the temp you want it to cook at. That makes no sense to me at all. Still, it does seem to hold temp well and stirs a very large bath. So far all we've been using it for is "safety cooking" pork chops.