here is my opinion on it.
if you are going to use 150 watts, as long as your tank is less than 18" tall you should be fairly unrestricted, if more than 18", then go with the 250w, if more than 24" look towards the 400w
the main difference in the wattage of
MH bulbs is there ability to penetrate into the depth of the tank..
also it sounds like Ocelot199 has already decided to go
MH, so it might be best not to confused the situation with details on
PC, as the details are not always comparable to
MH.