Your side speakers are going to be incredibly close to your listening position. I would say no on putting any speaker on the floor. I understand that you're trying to set your sides up so you can cut down on the direct sound. You might wanna consider getting dipole/bipole speakers for your sides. Even with distance adjustments your side speakers may be easy for your ears to locate simply because there will be no room ambient sound from your side speakers like there will be from all your other speakers which will most likely single out the side surrounds. Dipoles have a null that will greatly minimize direct sound which is a much better and clearer way of setting up near field surrounds than placing them on the floor.
Your system can shine no matter what it's made of.......except if it's Bose.