For those receivers that give you the option of setting speaker distances from the listening position... how do you measure them for multiple seating? EX. I have a long 3 person couch. It is easy to measure all speakers to the center of that couch, but wont my sound be a little off, even in the slightest degree for those sitting to the left and right of the listening position? What I thought I could do is measure the R main, and R surr to the right listening position, measure the left main and L surr. to the left listening position, and center channel and the sub to the center listening position. Sound like a good idea? Is there another technique for doing this that'd work better. Or should I just measure from each speaker to the center listening position and stop being paranoid?