[Delphinus]

From what I understand, they give off the best blue/white combo light with the most PPFD on the Bluelines, and the Bluelines draw the least amount of current, so these are the most efficient ballasts. But availability is an issue, there aren't any to be bought anywhere at the moment! Supposedly a new batch is being worked on and will be available "real soon now."

So the next best ballast is the PFO HQI's. Not quite as efficient, but almost, and can easily be bought since availability is not an issue. And some say the they like the light better on the HQI's, so there is probably a matter of preference there, hard to tell without seeing both setups in person.

I guess the Radiums on a typical M59 ballast and they're just blue, so probably not worthwhile investing in the bulbs if not going to invest in the ballasts as well.

Sanjay had a good article on this this some time back, "Do Ballasts Really Make a Difference?" Something like that. Can't remember which one it was now! Darn, sorry.