The K7 is a nice speaker. The difference between it and the K17 is the K17 has a better tweeter. Both are nice speakers. My setup used to be K7 center, K5 L/R, & K4 surrounds, before I started upgrading. They are great sounding speakers for their size. Bear in mind you must use a subwoofer with them as they are a 4" speaker and aren't rated below 80hz. These are rated for 200w at 4ohms and I found them very easy to drive to loud levels - still sounding great.
Some people find them to be a bit bright, personally I like the way they sound and still have them in my bedroom. As you can tell by my signature, I like M&K. If you are going to be near their HQ, I say go by and check them out for yourself. Or see if there is a dealer in your area and try them there.
I don't have any personal experience with the other speakers you mentioned. I believe that axiom has owners who will allow you stop by and check them out if you go to the forums on Axioms website.
Jack