I use the Mega 16/15/x SERIES. They are direct replacements for 400s. You can buy them from Hobby-Lobby.com.

Using Motocalc a Mega 16/15/5 will deliver the 128 output watts. But MotoCalc shows that the prop is stalled. So it will not work.

Can you increase your prop size to a 6x4? That will get you 128 watts out. Your 18 amp controller will be close to its upper limit. Too close for me to use.

If you can increase your prop to a 7.5 x 4 you will get about 190 watts out on the 16/15/5. But you will need a 35 amp controller.

Without a gear box it is going to be hard to deliver 150 watts and use the 18 amp controller. Using a gear box would require a bigger prop.

What plane are you going to be flying?

The Mega motors are not consider cheap at a cost of about $90 each. But they are a great value.

Hope this helps.

bob