To further muddy the waters, the amp/watt load is dependent on the size of the prop, battery pack voltage and the ESC. You can have a 600 watt motor, and only get 250 watts out of it with a smaller prop and battery combination.

One of the ways I determine the size/power of a motor, in comparison to a glow engine, is to use the scorpion comparison chart. I look at the E-Flite motors which have a glow conversion number in the name. Power 15 power 25 power 32 and so on. There is also a really cool calculator that scorpion has for their motors, the link is below. It lets you pick your voltage and a prop, and it'll give you all the specifications like static thrust, pitch speed, amperage, temperature along with many other useful facts.

This is a motor comparison chart-
http://www.innov8tivedesigns.com/Sco...ison%20Web.htm

Same motor comparison chart in a pdf file-
http://www.scorpionsystem.com/files/...rison%2001.pdf

Below is a link for a zip file that had the motor calculator I was speaking of. (very cool)
http://www.scorpionsystem.com/files/..._Calc_v341.zip

Below is a sample picture of the calculator program using a 3020-890 motor with a 4 cell lipo and a APC 12x6 prop.

If you look at the picture, you can see that this combo makes 108 oz of thrust at 57 mph. The amp load is 50.3. I love this calculator!