Hi Kore
If you have a 5 channel system (2 fronts, 1 center and 2 rears) then I think the best orientation for the rear speakers is mounting them on either side of the listener (should be called side speakers) If your sub is large enough you could use it for a coffee table, could blow the chips around the room though.

Enjoy the Music. Trust your ears. Laugh at Folks Who Claim to Know it All.