I have heard good things about Kumon from friends who send their kids there. We actually use the kumon workbooks with my 3 year old and I have seen a lot of progress in his skills. I also believe there was a thread on the Kumon method (
http://forum.brillkids.com/teaching-your-child-math/the-kumon-method/) if you want more info. Can't say anything about E.nopi math though, sorry.
Lindsay