@ozzy - I'd recommend trying the planar speakers with your current room acoustics setup to start with and see what you think. I've found that I prefer diffusors behind my dipole speakers without any absorption, but every room is different and some people have found they prefer absorbing the much of the backwave.
After getting them set up, I'd try removing the Stillpoint panels behind the speakers and seeing if you like the sound better. If so, this probably points to switching to pure diffusors.