1000g+? Im a little nuts, but Id go a bit higher... like 8x 6200's. If you make 'fake overflows' in the two back corners of the tank, each about 8"x10" each with 4 holes to pop the tunzes into, you can have two tunzes facing front in each box, and two facing to each side. Then, the flow can alternate between the two front facing tunzes in one box and the two side facing ones in the other at once... to the other 4 tunzes and back again. In this manner, with a long enough delay between switching, the tank will have a gyre effect... the flow in the entire tank will spin one way for a minute or two, and then the other way. By aiming the powerheads so they work together, you can achieve a whole that is greater than the sum of the parts.
The Aquaconnect 400's are a fine choice.
Ill have to look around for examples of what I mentioned about the Tunzes behind a false wall... I know they are around here, just have to go out and hunt for them.
You know, I bet it would just be easier to post a thread asking for people with them to post pics.
One I do know of is Iwan's. His Tunzes are hidden by special reef ceramic rocks. They are rocks shaped like mountains, and in the tops where they are close to the surface, there is a little box made of rock that holds the tunze in place. This is pretty cool because from the front of the tank, you cant even see the outlets of the pumps unless you look at odd angles. Heck, even the overflow is almost completely hidden...
http://www.hausriff.ch/4534/156972.html