First off, you are a pioneer of sorts, great thread. Browning out is to expected I would have to say and could be the result of 5500K sun light hitting the corals and not the 10,000K-15,000K light of your tank and in the deeper waters of the ocean. A good idea might be to grow out your corals in the green house and then move them indoors for a few weeks to color them up before you sell them. This will serve two purposes: 1) Get their color back obviously for better sales prices, 2) Get them used to indoor lighting again before you sell them so they adapt more readily for any customers that you have. One more thought that I had, instead of adding a geo-loop, why not install a couple 55 gal plastic drums in your basement (if you southern boys have them) and then connect that to your system. This will add about 100 gallons to the system and give you more thermal stability. Also, you can use the more constant temperature of your house to heat/cool the tank.
I skimmed through the last couple of pages to post, but are you having any troubles with the general lack of nutrients and the growth of soft corals?
Again, keep up the updates and post pics when you can.