So is the tank height is about 25"? If so, 250W halides would offer better penetration. However, considering you're only doing softies, I think you do have a fair amount of lighting. What are your metal halide bulbs (brand, kelvin rating)? How old are they? How high off the water do you keep the bulbs?
Unless you have a chiller already, swapping up to 250W halides might require you get one.
Agreed.
The Icecap 660 ballast can operate up to 16 lamp feet with a total of 464 rated lamp watts-- You have two lamps that are 6' each, which is 12' of lamp length; you're already at the max, I believe.