Have a look at Trident Engineering.

Try www.maxonmotor.com www.micromo.com , with these, you can't go wrong.

You can also try these guys http://www.groschopp.com they even have webinars and but they may not have a better range of motors than the others mentioned already.

I am myself after around a 2KW DLDC motor myself but I do not even know where to look for it as they are all seem to be much smaller.

http://www.danahermotion.com/ does manufacture BLDC motors in that power range.

On the other hand, try www.globalspec.com for many more results.

Very nice motors can be found at http://www.E-flightRC.com. One caution, however. Even the best made, and most efficient motors dissipate some heat. Small package envelopes will tend to run hotter. It's up to you to decide how you are going to dissipate the heat. NVH applications can be more difficult than model aircraft.