For anyone out there considering either building a router or modifying a router with one of the Chinese spindles, I bought a motor with VFD for $523.00 including shipping from China. They advertised 3 to 5 day delivery, but mine actually took 10 days (but still not bad). Here is my recent experience:

1) The motor works great
2) It is much quieter than a router (I was using a 3 1/4 HP Porter Cable)
3) It is still not 'quiet'. The pitch is higher than a router, and my wife finds it more annoying than a router, but I CAN listen to the radio while it is running, which I could NEVER do before.
4) I have the water cooled version, for which I used a fountain motor from HD. I first bought the cheapest one ($18.00), but it couldn't handle the head pressure from 50' of 1/4" poly-tite. I ended up changing to another fountain pump ($39.00) which seems to be working fine. I circulates with no problem and the motor stays cool (room temperature). I mounted a container up on the wall with the pump in it and it is working fine..
5) You can download a pretty complete VFD manual to help set it up, and mine came with instructions for the NECESSARY settings for startup. There are others that need to be changed, and I found the settings online from other users.

If you have any questions or problems getting it set up and working I will be glad to tell you what worked for me.

Ken

All in all, it was a VERY worthwhile upgrade, and I would recommend it to anyone using a router for a spindle.