The quietest sizeable chiller I've ever seen are the one's we use at work! PolyScience makes a line designed for chemical baths, laser applications, etc. They are re-circulating, or, as we use them, w/ a refrigerant and heat exchanger inside the device (sump in this case). We have.. 6 of them now at work (just installed another 3!), and they truly are a tank.. in the 5 years I've had the original 3, I've never done a lick of maintenance to them (other than clean the dust-bunny's once a year). You can't hear them running, even when sitting on top of them. I happen to have an extra 6305 (1/3rd horse) in my garage, if you're interested. Freight might not be cheap, but I can make it reasonable for you. FWIW, this fits in the "Price is no object" category, as they retail for about $2400.00.
- Mac