So I Just bought a 400w hps, I currentkly have 2 150w MH's. So my question is when I start my new grow should I veg using the 150w mh's or the 400w hps or should I get crazy and use the 400w hps and one of the mh.
Depends on the size of your grow. If it's small you don't want to spend more on electricity than you have to. If it's big use all the lights, the hps won't hurt your vegging.
My grow space is about 3x3.5 and about 6ft high. I want to squeeze as many plants in there as I can. eventually that room will only be for flowering and Ill have a separate clone/veg room.
Changed my mind on a few things, my grow room is actually a little bit bigger than I thought and I decided to use the 400w hps and the 2 150w metal halides, I figure I can fit more plants and there will be a greater spectrum of light.