Phyl said:2x250 would be WAY overkill. And the heat would be disasterous. T5 retrofit parts would give you the most upgrade flexibility later.
I apologize Buffalowing for giving wrong info.
I'm going to have to stay away from this thread. I thought you were doing a 75 gallon but its running freshwater fish (that is strike two). I was at work when posting. Trying to read, post and work at the same time is not working.