Lumens mean nothing to corals if the light source does not have the correct spectrum. A lot of factors are involved as well, such as photoperiod, water quality and clarity.
Kelvin rating is also irrelevant, but generally, light in the blue spectrum would be the most useful and moat efficient and growing corals.
Here's a good (but still basic) article about lighting:
http://www.successfulreefkeeping.com/le ... hting-101/For further reading, jump here
http://www.advancedaquarist.com/2012/10/aafeatureand here
http://www.advancedaquarist.com/2013/12/lightinghttp://www.advancedaquarist.com/2009/5/aafeatureA good way to know if you have enough light is to measure PAR. But since a PAR meter is very expensive, only a few here have it. But you can still have a crude estimation of PAR by using the formula here:
http://www.apogeeinstruments.com/conversion-ppf-to-lux/Convert the lumens first to lux then follow the instructions on the site. It is not totally accurate but it can give you a good idea if your tank has enough light.
Generally speaking, light demanding corals are fine at 200-450 PAR. Some can even grow fine at lower values.
Hth