Personally, I feel that gallon-for-gallon, a 240 gallon aquarium could cost the same as a 135-gallon. The tanks only 25 inches deep, so you could easily get away with 4x250w halides, or even 12-16x54w T5's(I would go this way to avoid chiller costs), a large sump with moderate flow (say, 1000 gph), then push the rest of your flow with prop-driven pumps like vortechs or tunzes, even koralias. Personally, I'd put a vortech on each end, then 2 koralia 3's (or 4's) on the back wall towards the middle, and you should be set. That would get you around 9000 gph, which should be more than fine for a tank like that, and you're still not that high on the energy ratings.
There you're looking at probably <1 kw for lighting, < 1/2 kw for circulation, < 1/4 kw for skimming/other filtration, and if you look into efficient means of cooling (assuming you'll need cooling rather than heating), you could probably run a 240 for around $150 a month. The initial set-up cost will be significantly more expensive, but proportional to the gallonage, as will be the costs of upkeep. Go big or go home!
