DIY LED Light Questions

[Beanz]

Hi all, so i want to build a LED light fixture for my new 45 gallon tank. I have now decided that i want to keep SPS corals in the tank. I don't really know all that much about the PAR, lumen, lux stuff that the SPS will require or how to achieve these amounts with LEDs. Anyways i will come back with more questions but if someone could please explain these things to me that would be very helpful.

Thanks, Ian