I am in the beginning phases of an addition for a home theater. I have begun to assemble some new items to go along with my existing A/V equipment. My existing speakers are KEF KHT5005.2. I am adding two speakers to make it a 7.1 system. I recently purchased a set of KEF Ci60.2FS in ceiling speakers for the rear channel. Today I got a killer deal on a set of Proficient W670 in wall speakers. I would rather use the in walls. I am always reading how the speakers need to be matched and for fronts I would tend to agree but for rears I am not too sure. Any suggestions?