Going to move my Polk Monitor 50s to rear (side of couch) for my 5.1 setup. My question is, do I need to elevate the speakers? Or can I just set them on the ground next to the couch? I also though about putting them about 3 feet behind the couch next to the walls. Opinions/suggestions? I am replacing Bose Bookshelf speakers that I have on stands next to my couch that face the person sitting.