I use a wine fridge I bought off Craigslist for $50.
Herpstat thermostat.
11" heat tape.
2 computer fans to circulate air.
All-in-all...less than $200. Holds 6 clutches in standard 6 qt. tubs. More if I got shorter boxes.
Mine is at the end of the video.
http://www.youtube.com/watch?v=gnEo1X40SPc