If these 12V LED strips consume 14.4W/m that means 14.4/12=1.2A/m 5 meters will consume 6A of current @12V. I would recommend a power supply which would not be loaded to a 100% of its rated output current (unless the supply is rated for 6A continuous current). But in this case, since you are not using the full 5 meters, the 6A supply will not be 100% loaded, so it should be fine.