OK, now I bought a spindle as well. I went for air cooled. I think that it will be the best for my needs. Been considering between water and air cooled, but have seen quite a few comments about leaking Chinese spindles so I decided I am not interested in testing/fixing spindles. If in the future I regret this I can always buy a water cooled one.
This is the spindle I bought:
CNC Four Bearing ER11 1 5KW Air Cooled Spindle Motor Engraving Milling Grind | eBay
So, now I have a lot of new toys to play with during and after the summer.