to be honest, i think a lot of the bulb stuff is hype. i'm sure you'll be pleased by any 400w HPS results.
with that grow space you can greatly increase your yield by letting your plants grow a normal vegetative cycle - like 2-3 months. I saw your plants are wide - that is one of the things i look for in a grow. short and bushy! The trick is to make sure as much light hit your bud sites as possible without hacking the shit out of your plant.
here is an example of lollypopping (cut away all the undergrowth to focus light and the plant's energy on producing buds) before and after.... |