I have a Klipsch KSW12 sub. It is downward firing, but it has a port in the rear. I keep it just a few inches away from the corner wall, because it gives a nice oomph to the bass. I have read that Klipsch bookshelves and towers should be kept at least six inches away from the back wall because they are rear-ported and placing the port too close to the wall will negatively affect the sound. Would the same hold true for my sub?