I am building a quadcopter as we speak (my first) the airframe is coming along nicely, but I have held off on the motors.  I have been comparing 3 Turnigy motors

Park450 890Kv 14A

Park480 850Kv 28A

Aerodrive 920Kv 16A

I have been using the xcopterCalc and I found some results and questions at the same time that I would appreciate your thoughts on.  In general I have been looking at a basic quadcopter but would love to be able to carry a heavier payload in the future (like a mirrorless camera).  When I plug in these motors I find some expected things and unexpected things:

1) It takes roughly the same power on all motors to hover - which just tells me all is well in the world of physics :)

2) The system seems to tell me that a larger prop is better.  I was thinking a 13x4.5 slow fly but that is because it is what I see others use rather than any science...  I could use a couple pointers here and maybe some real math.

3) The 28A motor seems like overkill, but as I look at the charts it seems better in all cases - do I need twice the torque at a given RPM, does that mean that i should use a larger prop?

Finally, if anybody has thoughts on the motors above, I would love them.  They are all less than $20 which means that I can lose my quad and not break the bank... well except the APM part.

For those that want to see the motors I am looking at, they are below...

https://docs.google.com/spreadsheet/ccc?key=0Aiell8oyK_YsdFFadmVPVG...