I been having a bit of a read of the Chinese spindle thread and from what is being said there the cooling requirements aren't that hard to meet.

I'm currently thinking of mounting a radiator on the back of my gantry with a small pump on top thus limiting the pipe run and total water volume. I was thinking I'd probably use a modified computer cooling system. As Jonathan mentions in this post the dissipated heat is probably of the order of 110W max. Cooling systems for CPUs have to be able to deal with 80W and probably quite a bit more because people using water cooling are often over clocking. If you are willing to run with a reasonable delta temperature (between ambient and radiator) passive cooling should be quite easy. If you want a smaller delta then a 12V computer fan run at 7V would provide good air flow over a radiator and be essentially silent.