I am about 12-14' from the mains.
With that much separation between your mains and surrounds and your surrounds being so close behind you it might be hard for any speaker to created a really smooth transition from front to back. I think you would benefit a lot from experimenting with placement and if possible moving your seating out off the back wall a little. Don’t get me wrong, it’s going to sound great but with tweaking a bit you might be surprised how much better you can get to sound.