As Josh said, the icecaps ballasts are very versatile, but if you can get a good deal with magnetic ballasts like the PFO retros, don't pass it up. These ballasts can run most of the popular bulbs, and if you have VHO for actinic support, you probably won't need the high temp bulbs that need the HQI ballasts. The german 10k, (ushios) are available in 250W and 175W, but as of now, iwasaki doesn't make a 175. (I heard they're coming out with new bulbs designed to run on mh ballasts, maybe they'll do a 175)

Matt