The arrangement of the drivers on the PC2000 causes all kinds of problems, definitely skip them. As for the height above the listening position, 5 to 6 ft above is certainly not ideal. The side surrounds and read surrounds should be at a height level with the ears. See the
Atmos installation guide. The PM1000 is probably fine. If it were me, I would look at more controlled directivity speakers if you are going to mount these things next to a wall. I would be looking at some Klipsch RP speakers, Hsu speakers, JBL Studio 530s maybe. The wall is going to be an unfortunate source of diffraction, but that is going to affect wide dispersion speakers more than narrow dispersion speakers. If you really have to mount the speakers high, maybe look at the SVS Prime Elevation speakers.