Pretty impressive. Congrats on getting that beast up and running!!
What I am trying to discern, is if there are real advantages to running say 5 (fairly expensive) 315w lights, when compared to simulating the spectral output of CMH with for example 2 DE 1kw lamps paired with supplemental 1000 or 600w Ushio Opti-Blue or similar lamp to cover the rest of the spectrum and end up with something similar to 3100k CMH in terms of total spectral output in the room. This is where we need a side by side comparison. We all know that running full spectrum lighting is going to produce a better product, so comparing to straight HPS (while informative) is not really an apples to apples comparison. Since so few people seem to be supplementing their HPS its difficult to come up with the justification for investment in CMH to replace something like this, since they should be fairly similar quality of light. Given that, (which is not a given, but a speculation) I would further speculate that the 3kw of DE HPS/Opti-blue could potentially produce a similar GPW with similar THC% as the 1575w of 3100k CMH, covering the same area like you are doing. The real difference is cost. In my estimations, it would cost significantly more to get just over half as many watts.
CMH is supposed to be more efficient at converting electricity into usable plant light, so the question then is how much more efficient, and is it worth spending big $$ on. It may be that the savings would come more from decreased cooling costs, so we have to take that into consideration as well. We have to consider the total draw of the room, when doing a head to head comparison.
From what I understand, 1.5 gpw is attainable with plain DE HPS. when you throw the supplemental light in there, the actual GPW might be slightly less, since we are counting watts, and like
@Merlin34 said the 6-9% thc level increase is what the supplemental light will be primarily doing for you.
Hopefully someone out there has the time and resources to be able to do a real comparison like this.