Jim,
What do you want to fly and how do you want to fly it? I have several different options and just need specific info to guide you to what you will need. I flew the X-Wing on a $5 Emax 2805 2800KV using a $8 Tower Pro ESC and $8 Zippy 1300 20C 2S pack. It turns a 5 x 3 Cox 3-blade @ 12-13,000 rpm @ 13 amps. I charge the 2S packs 2 at a time on a Hextronic 8080 charger that cost $27. All this is available through Hobby City.
Now if you put 3S 1100's on this motor, it will turn a 4.7 x 4.7 @ 18-19,000 rpm @ 19 amps. This would make screamin setup for a 1/2 A combat model on either 35' or 42' lines.
Another option is to use a 2040 inrunner with whatever Kv suits your specific needs. They offer them in 2080, 3500, and 4850. I have a 2040 2080 Kv & a 2040 4850Kv. I use the 2080 Kv in a Speed 400 racer on 3S and fly on a 5.5 x 4.5 prop @ 13,000 rpm pulling 12 amps static. I use the 2040 4850Kv motor in a EDF on 3S and it absolutely screams at close to 50,000 rpm. I ran it up on a 4.1 x 4.1 on 3S and it was screaming and pulling 25 amps. Not sure of the rpm but it was around 30,000 by sound.
In-runner by nature will be more efficient, but are a bit heavier in an oz/watt out comparison. The Emax 2805 2800Kv weighs around an oz and complete with battery and ESC you are looking @ 5.5 ozs total ready to put in an airplane.
Archie Adamisin
Muncie, Indiana