Hi Sandy,
I suggest Googling your post's title to find some of the tradeoff's, especially from home theater installations. Your sub weighs almost 60 pounds, so you'll need a sturdy shelf if you put it on one, but also expect that it really should be sitting on the floor. My earlier research seemed to indicate that "it all depends" on the playing space and its acoustics, and your own ears will be a major part of determining where it works best. Of course, moving a 60 pound box around and having sufficient cable to reach it can be some work, but I guess that's all part of the "fun"!
The low notes the sub produces tend to lack a sense of direction, ie, the ears don't really pinpoint where the sound is coming from. My sub is located on a side wall a few feet in front of my main speaker array, which I face when playing (so the sub is to my right) at about 1/3 of the room depth distance. I share it with my home theater, for which it's along it's front speaker/TV wall (the home theater receiver balanced all of its speakers, including the sub, automatically).
My biggest issue with my sub was not so much the placement, but the fact that I had the loudness set too high, so I was exacerbating the standing waves in my living room for the low bass notes. I used a Radio Shack sound pressure level meter to get it set correctly, along with balancing my other speakers accordingly, and that made a great (and beneficial) difference.
Barry