I was going to mention that You had the uses for MH and
hps backward, but I guess you have that figured out. I know a lot of people like using water culture for growing tomatoes, and even though I have grown tomato's in a flood and drain, I would prefer using a
drip system for them myself (as well as most large plants). A drip system is easy, and much more forgiving.
P.S.
Have you considered florescent lighting for lettuce?