You'll come close enough just choosing two motors good for 250W each.

Smaller motors tend to be designed for fewer cells, with higher Kv ratings.  Ditto, it'll be harder to get smaller ESCs with higher voltage ratings.  So you may have to go with more mAh and fewer cells.  This won't be as big a deal if you put the batteries in the nacells with the motor & ESC, but may require your attention if you want to use one battery in the center.

Do you know how to calculate the pack total energy from the capacity and cell count?  Just keep the total battery energy rating the same, and you're good to go.