Make sure exactly what you want to keep long term before buying lights. You can start at Power compacts and work your way up to VHO, T5 and then metal halides as far as intensity goes. If you are positive you will stick with low or medium light corals something like an Orbit 4 x 65 PC fixture would be fine.
If you want high lighting critters like SPS and clams you need to look at the other lighting, preferably the halides.