Hey Blazed Hippie, I was where u were not long ago at all. 1 of those 150 watt HPS will do you just fine for 1 plant. Yes you will have to keep it 6-12 inches from the top of the cola, and you WILL HAVE MUCH BETTER RESULTS, using a screening method, to grow your 1 plant sideways. It will give you a even plant canopy which allows all the buds to get equal and adequate lighting, not just the cola at the top. You will yield more and have better quality over all. You just wont have the one big bud, you will have many small and middle sized ones. Also, you will find you can still add in a few CPF's just to get even more spectrum coverage and even slightly better buds and coverage.
Hope it helps.