Hey K3nv,
Sorry, I was out all day and am just getting back to it.

The site you showed is very similar to DriveCalc, which is found at DriveCalc.de (I think). DC is very similar to MotoCalc which a paid for program. What these programs will tell you is what your combo will do. It is hard to imagine what values your airplane will need, and there are just so many factors in designing for them, that we just need to start somehwere. Like you saw, when you increase the kv the speed goes down. Weird huh? Well, it may be that you are loading up the motor more and it is getting "bogged" down. That is why we shoot for the %80 efficiency where most motors run best.

Seriously, if you give me the exact Turnigy or Hobbymate or Icecold motors I could give you a few screenshots and combos real quick like. Just pick a few motors to try to get the hang of it.

The important numbers that the programs will give back are the speed and the thrust. Generally we want to fly at 3x the stall speed. Trainers fly slow (maybe stall at 15-25 mph), where a jet might stall at 50-75 mph. So if you want to cruise then pic the appropriate number. One of the funny things you will see is that as your stall speed increases, generally your thrust to weight ratio drops. On a slow stall trainer or even a 3D machine, the thrust is high, where a jet might just have the thrust to make speed(but not accelerate very fast).

Hope this helps. Feel free to send me a PM or post here and we can continue the discussion. Real numbers will help a lot.
Curtis