Question about Klipsch R-820F

If you have an option, why don't you go with a nice pair of shelf speakers on a stand. This will take up alot of space plus you won't be using it to it's full capability. However, most amps you can switch front and back channels. For example if you're home is set as an open plan you can use then back speakers to direct the sound to the dining area for example. Then this would work excellent as a rear channel

I don't see any problem.
You'll need to adjust the bulb settings to balance the sound properly.

Basically yes. However, this does not depend on the loudspeakers, but on your amplifier.