Just an update, I went with the Current Outer Orbit 2x150W MH + 2x130W PC fixture.
Yesterday, the house hit 76 degrees, and the tank spiked up to 86 degrees around hour 4 of the metal halides being on. I put one of those oscillating house fans behind the tank today and timed it to only come on when the lights came on. Guess what...tank is steady at 80 degrees, where I have it set to be. No chiller! Weeeee!