The K9C is ready to be used as a Mobility Express AP. The K9 requires a controller or be a subordinate to a ME AP. You can always convert the 18xx to ME or have it join a controller.
The Mobility Express guide has the information on converting and setting up ME:
http://www.cisco.com/c/en/us/td/docs/wireless/access_point/1830/quick/guide/ap1830getstart.html
-Scott
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-Scott
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