Most likely any reciever around $500 or above should be powerful enough. I had no problems driving my K7's and K4's (both 4ohm) from a Denon 2802. Currently, I run 4 ohm speakers from a Denon 2805 fine. In my experience, the smaller M&K speakers are not terribly power hungry. Some of the larger (S150) speakers seem to crave a little more juice. If you're not sure what will run them, call or email M&K. They have always been very helpful to me in the past.
Jack