if you can solder you can make a DIY light, it is simple. here is a link:

12 Premium LED Do-It-Yourself Retrofit Kit

i would go 12 leds and hang it roughly 10-12" from the water surface, you should be able to grow pretty much anything including sps in the tank with those over it. you can always have the light lower if you want more power. use 60 degree optics.

i have a 5.5g frag tank with 6 LEDs on it DIY retrofit and i can put anything in it.

you can get a heatsink with the size you need from heatsinkusa.com