If you are looking to do some serious coral growth, and want to experiment, retrofitting LEDs are the way to go IMO. Let me just get up on my
real quick...
-They are pretty costly upfront, but put out more then MH at about half the wattage, saving you money on energy bills long term.
-Fully adjustable blue/white balance so no messing with bulb configs to get the right color temperature for you.
-Diodes have a lifetime of 50,000 hours, meaning you could run them 12 hours a day for 11.5 years before worrying about changing them out. Compare that to changing a MH bulb at $60 every 8-12 months.
-Almost NO heat given off and are easy to put in tight places, can mod into your existing hood and will probably drop your tank temperature.
-there are some awesome DIY projects that people are hooking to them to fully automate their light cycle, sunrise, sunset, all sorts of fading in and out.
ok..ok.. off
Alternative options would be
MH-
Viper K-2:
I would suggest the 150w, they are a great fixture, I have the 70w, get pretty warm as expected but very easily adjustable to get the right height off your tank without transferring too much heat.
Sunpod:
These have been discontinued as far as I know, but were a great little fixture if you can find a working one used. Very clean looking.
T5:
UVL is coming out with new shorter bulbs at I think 12" and 18". Nanotuners is first in line for them and have been working closely with UVL to develop fixtures. They have one for presale which is half LED and half T5, pretty costly but it looks really nice.
Probably more information then you wanted..but there it is. Feel free to PM me if you have any questions about LEDs, I just finished my own retro on a JBJ 12.