Wow, a PID-controlled melting pot project sounds like just the thing to do this winter.
If your not overly handy with that sort of stuff there is also a fellow who was selling the completed units in the Vendors Section at CB's. Not sure if he still is or not.
Also when/if you do put one together yourself, when you get ready to test it out, don't simply hook up your V meter to the leads and think something isn't working right on the output. Plug in a lamp and then test it out. They control the amps/watts not the voltage so you will always have a volt reading. Just a heads up. Also some recommend getting the 25amp relay verses the 15. I have had the 15 and so far it has held up fine over the past year and a half. Of course when I pour I pour in bulk so it takes me a while to get back to pouring again. The more cycles it does the shorter the life has been what was reported. Anyway just a few tidbits I picked up while researching them and building mine.