MH 600w to 1000w for autos?

All Ive ever grown was photos. I've decided to give autos a try on my next grow. Fastbud seeds, Gorilla Cookies, Wedding Cheesecake Cake and Blue Dream.

I upgraded my HID light and ballast from 600-1000w. Ive heard from a few sources that with autos it's a good idea to start using a 600w bulb from germination and veg, then switch to a 1000w bulb just about the time they go into flower. BTW I have a dimmable ballast.
The theory being the super intensity of the 1000w bulb will really produce hard, sticky buds.
Thoughts?

DLI

Auto's don't require as much ppfd because the photoperiod is longer

Hps be better than mh for flower but ya do 600 till flower then 1000 for flower