Terp tom, Gavitas DO NOT fall into the 50wpsft rule of thumb, people are lighting up 4x6 (i have heard 5x5) areas instead of 4x4 with 1000w gavitas. Lots of folks seem to burn their plants from having the lights too close.
HTH
These folks are not paying attention to their plants, i've done air cooled, bare bulb and now Gavita which is now my personal choice due to the penetration, i do, however, keep my lights 36" from the canopy.