Something like this would probabally do the trick,
http://cgi.ebay.com/ws/eBayISAPI.dll...868610838&rd=1 the servo's I have on the Excello mills I have (8x36) are 26"lbs DC motors reduced by about 2 to 1, but that would be the largest you should require. It depends on the demands you place on the mill, servo's are the way to go, but obviously stepper are more cost effective.
But if you go the ebay route, you can level the cost difference out somewhat.
Al