Mogul socket seems to be the best way to go over 100w from what I can tell. Electronic ballast, being they are cheaper, not that they use less electricity.
-Edit // HQI seems to be more expensive as well, and im trying to keep it low on the price range. Anyone know what the difference between an HQI and just a medium/mogul based lamp? And would a ballast like so:
http://www.ballastwise.com/item.asp?...FID=17&level=1 work for an HQI bulb?