http://reefkeeping.com/issues/2007-04/jb/index.php

This site talk about the PAr of each bulb, got this from Garrett. It looks like XM 10 K has very good par compared to coralvue 10 K and 12 K. Who knows, I grow great stuff with my reeflux 12 K , but I do notice it is dimmer than the xm 10 K on my other set up.

-Joseph