[suicideneil]

1515 2.5d = 1650kv
1521 1.5d = 1900kv

I think you'd have to gear up the smaller motor a touch to get the speed you want on 6s a123, where as the larger motor would be about perfect with 'normal' gearing. In an emaxx weighing about 10lb, I think you'd be happier with the 1515 2.5d, or perhaps the 1515 2d- perfect balance of speed and power at 2050kv, and would work well on anything from 4-6s lipo voltages- gear up or down as required without sacrificing temps much. I wouldnt bother with current limiting via the esc either, sounds like a good way to hurt performance more than anything.