Glseye, yup I am in the process of my 400 gallon. the hard part is over. and its got water in it and is in the process of cycling. The first thing I would say is FIRST make sure where you want it and make sure that its gonna look good there. that was my problem. and most of all make sure the floor will support it. you have to realize that tank is gonna weigh over 2 tons when its up and full.
that is the first thing I would do and then research on pumps. I wold recomend doing a manifold system.
I would start there. PM me if yo have any questions