Dave, welcome. If the entertainment center that you propose placing the QSs on is upfront with the main speakers, that positioning would defeat the entire purpose of surround speakers, which as the name implies is to "surround" you with sound. As Randy(sirquack)pointed out, in a 5.1 setup the surround speakers should be slightly(maybe 2')farther back than directly to the side, to lend a little back effect in the absence of back speakers in a 7.1 setup. They should be directly to the side of the listening position if the setup is 7.1.
Yes, the bottom speaker in the QSs should be raised at least 2" clear of any obstruction to the sound.
