I am not saying that all the ballasts are the same or all the various brands bulbs are equivalent. I am saying that the bulbs that I use are good and I have no problem with using them. The corals, clams and anemones are doing well and I only pay 20 dollars each for them. Maybe we should bring this to Sanjay's attention so he can test these bulbs. I have paid up to 100 dollars for these various bulbs before and see no different in using them on my tank than the bulbs I am using now. Of course a 6500K bulb and a 20000K bulbs have different spectrum. Even 20000K bulbs from various company have different spectrum. All of this depends on the composition of the metals in the glass envelope that give off this spectrum when excited by the electric current going through the glass envelope.
All I am telling you is that for someone to determine the compositon of this mixture is very easy. Once some one come up with the "ideal" composition, someone else can copy it and there is nothing the original person can do about it.
What is "ideal" is debatable. I guess that is why you have various brandd of bulbs and why Sanjay tested each of these bulbs and give us the intensity and par value of these bulbs.
For me, I use my own judgment and experienence. I am not going to spend 5 times the money I need to spend just so that I get a bulb that someone else tested the spectrum and recorded it. Most likely, when someone set out to copy the bulb, they would copy the best on the bulbs (in their opinion anyway) rather than the worst of the bulbs. If I buy one of these copy bulbs, I would likely get the bulb that somebody evaluated and consider it is the best. Is my opinion is the same as this person? The answer to this question is unknow to me, but I am willing to chance it (for 50 dollars less per bulb).
About the ballasts, there are diffeferent in various ballasts, but I only have one type and I am not going to go out and buy brand "X" ballasts because someone test and say that it is better. I may read about this and use it when I am thinking about buying my next ballast.
Just my opinion, and my experience that these bulbs are good and work well for me for a very cheap price. Even at this price, they are very expensive in compair to similar bulbs that are not market for aquarium use.