i'm glad to hear there is going to be another tank similar to mine in the area. I have a 36x37x18 semi cube. I have tried several different lighting options over my tank and haven't been happy yet. I first wen with a single 250 with pc hanging fixture, but i didn't like all the shadows it created around the tank. I think you would have the same problem with a single 400 or 1000. Also, i'm not sure how your aquascape will be but i have a central lr island and with the single light it created one extremely bright spot in the middle or the rockscape that would get cooked by the intense light.
I then changed to a hanging fixture with 2x250 mh and 2x39 t5s. I really like the fixture, but i'm still not getting the spread front to back like I would like to see.
I think stephen hit the nail on the head when he said 4x150s in a canopy, but if you're like me you don't want to build a huge fixture to hang over your tank and ruin the asthetics. My next attempt is still the 2x250 mh, but i'm changing to lumenarc mini reflectors to hopefully spread the light out better. I have built a hanging fixture that matches my stand perfectly. In the end it will be a hanging fixture with 2x250 lumenarc MH powered by lumatek dimmable 400/250 mh ballasts, and 4x39W T5s in individual reflectlors for actinic supplementation that will be driven by an icecap 660 ballast. This will all be hanging and hopefully will not ruin the rimless look of my tank. If you'd like to come by and see my current light versus my new light so you can get some ideas feel free to swing by. That way you can do it right the first time.