Depends on your standards for sonic acceptability. I found the AudioEngine unit acceptable for surround and sub in my 2nd system.
On my first test of the devices I got noise and anomolies but I only had the sender and receiver a yard apart. When I separated them I got better results but still the wireless piece seemed to bleach the sound a bit. I'm hoping that if the bleaching is the only penalty, it will be ok for rears. Will try it over weekend.
Sounds like you are having better success in your second system than your first, yes?