The last entry in this linked thread shows how you can get quite a bit of cooling using a two-stage system. An item that I left out of the photo was a small fish tank pump that circulates the ice-water around the coils in the HLT. It makes a big difference. See it here...
My cooling system gets me to pitching temperature in about 15 mins. I use a KegLand counter-flow wort chiller as the first stage of cooling, with the discharge feeding an immersion chiller that I have sitting in an ice-water bath. If you throttle the flow rate with a valve as it runs into the...