A couple of things spring to mind.

The Kress weighs 1.7kg whereas the water cooled spindles seem to weigh around 5.5kg to 6kg. This additional weight, cantilevered out from your Z axis, will need a much more rigid machine to stop it flexing. Also, the water cooled spindle will be able to take bigger cuts, which also increases the loads on the frame.

Also, for your application, whilst you should get the quietest spindle you can, you also need to take into consideration the noise created by the bit cutting into the material.

Watch a few YouTube videos to see the difference between the bit cutting air and cutting wood.

If noise is an issue, it might be worth including an sound deadening enclosure in your designs from the outset.

Adrian.