Whole home needs

Have the whole home system..HR23-700 has the CCK...HR21-100 has a deca and HR24-500 which I recently found out has built in DECA...

Here is my question...If I eliminate the HR23-700,  can I also eliminate the CCK and still have the whole home package, or is the whole home package dependent on having the CCK?  If I just had the DECA's as noted above along with the internet what if anything for seeing other receivers  does that do?

thanks..