Jim sold me on the XM's and I am now using 3 over my 180g sps tank. JB NY on RC did a lighting study that shows the X<'s are on 2nd. in PAR to the iwasaki. To me that says they have more than enough PAR to keep sps happily. Here is the link to that study: http://www.cnidarianreef.com/lamps.cfm This shows a lot of different 250w lamps run on different ballasts and the PAR reading each had.

I am really loving mine and I am now seeing coloration shifts that are for the better. My purple plating montipora is a purple/pink that the colors jump out at you. It is amazing.