You can punch up the numbers using PCalc at
www.flydma.com. Keep in mind that it's only a simulation, and isn't 100% accurate. It's best for getting RELATIVE figures.
I was a bit worried that you were trying to run a 6V Speed 400 on a 3S LiPoly. That wouldn't work for long. A 7.2V Speed 400 will be okay, though.
To tell you the truth, I don't have the foggiest as to what prop to use on this one. What's the actual ratio for a D gearbox?