Just finished swapping out my 1.5kw water cooled spindle for a 600W air cooled. I found I was not using all the available power in the 1.5kw, and it was a little on the heavy side for the 60mm Z axis. I got a great deal on it from banggoood, here is the link to it:
https://www.banggood.com/ER16-Chuck-DC-110V-600W-Air-Cooled-Spindle-Motor-With-Speed-Governor-And-57mm-Clamp-p-1127094.html?rmmds=myorder
I only paid $227.00 Canadian for it, so approximately $165.00 USD. The great thing about this spindle is that it uses an ER16 collet, allowing for some larger bits to be used. And there is negligible run out on the spindle.
I had to make an adapter ring for my mounts as the 1.5kw was 65mm and this one is 57mm in diameter. So I made some 3D printed rings to adapt the spindle mount and dust shoe. I am very pleased with this spindle, but only time will tell if it will stand up to the intended usage. I can always go back to the 1.5kw if needed.