Depends on what company your looking to get these from.
Advanced lighting solutions is a good brand. Its a newcomer of sorts to the reef world, but its roots go ways back.
I have seen many companies try to pawn off these cheap lights. But you get what you pay for.
However there is a company(sorry name escapes me ATM) that makes something similar to what you are asking about.
It requires its own special hood and power supply. For 72" hood, they charge about $300. That sounds good...but you have to buy the bulbs separate. Ill get to that in a bit...gotta sweeten it up a bit before I sour it...
The principle is each hood has a computer controller that you can tell to light up individual bulbs, or groups of bulbs, and what times they com on and off.
So....say I have a bulb that matches the early morning spectrum of the sun. I tell the timer to do it from 8-10AM.
Then as the day progresses I change the spectrum again.
Now 12-4pm I have a bulb that best simulates the spectrum provided from an afternoon sun beam. So now the computer lights up another set of lights. Lets say I want a 10k bulb, and a 14k bulb going off together. I just tell the computer what bulb I want and it works.
I think you get the picture, but the possibilities really open up to what you can do, and what kind of color schemes you can give your tank. Its a truly remarkable the amount of customization you can do.
OK now that I made sound great here is the kicker:
the hood w/power supplies(or what ever they are called for LEDS...bukpack?) cost you about $300...no biggy.
The LED bulbs themselves cost around $600 each!
So if you want to max out your hood with the 8 bulbs it and its computer can handle....thats a bit of cash to spend.
I cant, so what I will probably do is order the hood, and maybe a 10k bulb to start. Then each month Ill add another bulb or two till I have a full set.
Anyways. Ill see If I can get you a link to exactly what Im talking about.