I found a place last night that sells 150w hps/medium base for $11.95...I didn't want to get too deep right off the bat, but chowder is right on...Fluoros can be put right on top of new plants to keep them nice and tight...I use fluors for clones/seedlings...400w MH for Veg, then the MH and a 250w HPS for Flowering.
Before you ask: Ebay or Inside sun has the best deals without a doubt...
I think I am going to buy 6 of those med. base 150hps and make an 900w flower chamber...I have to research if they last very long...