If you are going to count on a closed loop for your in tank flow I definately recommend an ocean motions type of device - either 4 or 8 way and a large external pump such as a Hammerhead to drive it.
I also concur with looking at running 4 MH over your tank and using a luminarc type of reflector.
And of course, with a tank that large you are also going to have a substantial cash outlay for live rock and live stock.
Another consideration you may want to look at is a chiller. With all the $$$ laid out in your equipment and livestock it would be a shame to have a heat issue with your tank that causes you loose it all (like I did last summer
).
As you have indicated that the tank will not be accessible from the back you may want to also look at some type of device to raise and lower your lights for easier access to the tank.
A good person to pm is probably Superfudge as he is a master at this sort of thing.
Good luck and please post a thread outlining your progress.