centimeters to inches - you divide centimeters by 2.54
inches to centimeters you multiply by 2.54.
You can buy ballasts, end caps, reflectors and T5 bulbs, wire them up properly and stagger them over the tank to get the whole 150cm covered. For a 40cm wide tank, you could fit five bulbs relatively easily.
If you like a more blue tank, use three 454nm actinic blue lamps and two 10,000K daylight lamps. If you want it to be brighter, use three daylights to two actinics.
If you have access to metal halides, you could put two 150 watt 14,000K metal halides over your tank and supplement with two 454nm actinic T5 lamps. But, that is only if you want to do LPS and SPS corals for your tank.
LEDs are awesome - if you can afford them.