Just remember when going from a 315 over a 3x3 to a 630 over a 4x4 that your loosing 2 square foot of growing space per 630 compared to 2 315s. (18 sq ft with 2 315s vs 16 sq ft with a single 630). Therefore if you wee changing the 315s for 630s, watt for watt,(which I can see that you are not)...