Just wait and see if you start vegging with a 400w MH what you end up with, and how fast...
I used to have a hard time getting my clones large enough to flower as a flowering plant was getting finished, but I was still vegging with CFLs and then flowering with HPS...but I got a 400w CMH for flower, and changed the HPS to the MH on the digi ballast, and man then I had clones that I was having to cut in half halfway through the flowering cycle because they were growing too fast...I got to where the schedule was take a clone and flower the mother plant, then veg the clone for a month (1 week to root 3 weeks of actual veg growth) and then I would clone that plant and toss the mother plant...then by the time one plant finished flower I would have a clone of the right size ready to go...I veg for 3 weeks and get 3 oz per plant...so that is awesome..but just imagine.