Need lighting advice

[Glennrf38]

My new tank will be 24 x 27 x18, which according to Albert talking to my wife is a 200 Gallon . Personally I think it is much closer to 50. But who is she going to believe, right? I think I want to go with MH for the look. I have read that 250W is too much power, but have been told that with it I will be able to keep anything in the tank. So once again I have no idea what to do......

So, do I go with:

150W
175W (harder to come by I think)
250W
or do I just give up and grow mushrooms?


Second thing is I am looking for a lower cost version ( ie used).

Thanks

Glenn