I would try the aluminum heatsink first. If that doesn't work out, I'd try building a simple cooling loop out of a heater core and an electric water pump. Using ethylene glycol and raising the pressure ~5psi, you should be good to 230F. If you build an efficient cooling system, the controller shouldn't reach those temps anyways.
I agree with others that the heatpipe is overly complex. If you do decide that route, I believe the working fluid is often alcohol...but I'm not sure.
- LostCause