It is unlikely you would go bigger but just in case I would get your equipment rated at 750 to 1000 gallons.
As far as skimmers go if you want a short skimmer I would look at My Reef Creations. They have a skimmer MR-3 Dual Stack Recirculating Skimmer that is awesome. I bought one from a guy, his was a knock off that he had built but it skims like nothing else I have seen.
http://www.myreefcreations.com/MR-3R-DUAL-Stack-Recirculating-Protein-Skimmer
Kalk Reactor I would use a Geo Reef 818 (I believe it is)
http://www.geosreef.com
Calcium Reactor I would use the My Reef Creations again
http://www.myreefcreations.com/CR-6-Dual
Closed Loop System I would use two Reeflo Hammer heads and two OceansMotions.com OM4 1 1/2" in and out
Return pump I would use a Panworld 250PS with 4 - 1" penductors set at 3 to 4" below the water line so you get mid and surface movement. You can also tee this off to feed your refugium / ca reactor / etc. if the pump is too strong for your liking.
Lights I would use the Lumen Bright 3 DE Metal Halide Reflectors 250W DE with a HQI ballast of your choice. I hear lumateks are good to go with. I would put as many as you can the length of your tank with 6" between each reflector to make sure your light over lap. For your actinic lights I would use Icecap 660 ballasts and four 48" T-5 each each ballast . If you overlap these your spread should be enough. I am guessing at using at least 3 IC ballasts with 12 lights.
I would get some sort of Aqua Controller for sure to keep everything stable for you. (On sale at reefgeek.com - $300.00 off for complete package)
As far as live rock, I would use base rock from Marcosrock.com If you email them and tell them what you are looking for they give you some great pieces. I have over three hundred pounds between 7 large pieces. Remember the rocks will come dry and when they are cured they will weigh about 1.5 times they were dry. Example 600 lbs of dry rock = 900 lbs of cured wet rock. Just make sure you follow their advice to cycle the rock. The reason I like the big rock is it is easy to stack. It goes together like legos or tinker toys. Once you have your might set on the aquascape you can epoxy them together. You never have to worry about a smaller piece falling and hitting the sides of your tank.
Sand you can also get from Marcosrock.com. It is a fine sand but if you have your closed loop pushing from the bottom up the sand will stay in place.
If possible I would suggest to stay away from powerheads. Yes they work and the cost to run them are much less but you will not be happy when they blow sand all over the place.
Plumbing I would use as much spa-flex hose as possible avoid 90 degree elbows. Once you get everything plumbed do a leak test and run the tank with fresh water for 24 to 48 hours. This will also help with the glue from the plumbing.
Hope this helps
