There are too many answers to this question! I personally would go with 4 high output T5 fluorescent bulbs, and about 21 3 watt royal blue Cree, or Luxeon LEDs. ATI is a popular brand of T5 tubes. If you ever advanced from soft corals, you could still maintain them with this lighting by adding another strip of royal blue LEDs. As I said, this is just one of many preferences. Some will point you to LED fixtures, but be warned that you should see lighting in operation before you make your purchase! Not all lighting is equal by any means! And a bargain fixture with lots of features is worthless if you end up not liking what you are looking at!
I've built 4 rapidled fixtures and I wouldn't say I absolutely love them but they look great depending on how you arrange the leds which is easy to change. Only reason I don't absolutely love my fixtures is I know there's better setups out there but that's the case with everything lol
A basic DIY LED fixture like my gu10-based light would light a 55-gallon tank for about $140 or less.
I would at least consider this approach before you commit to a mercury-based (short bulb life) light such a T5. In the long run T5 is extremely expensive.