coming from a fluorecent person, a 400 watt HPS should work...depends on how many plants you have...being a fluorecent person, I made a 350 watt fluorecent fixture using T8's and it worked for my tomatoes...

-j-

how tall did you grow your tomatoes? light cycles?

Either halide or HPS would work. Ideally a combination of both, but a Hortilux HPS or Agrosun MH would probably give you the best color spectrum and best overall growth and fruiting. The plants would LOOK better under MH, but probably give better yield under HPS.