What is the BEST solution to the IR problem where the receivers have a "behind the wall" installation? (3 receivers)

Are you trying to reuse your current remote? If so then you could just get an IR repeater. If not then you could get an RF remote and extender.

I already have two RF remotes (DirectTV & Bose) so I would just use IR. How does the repeater work? Is that the same as the "Cube" things? If so, which ones are considered to be the best to use (less than 100'). Thanks

Have a look at this post.http://www.avsforum.com/avs-vb/showthread.php?t=850354