Putting your components inbetween your speakers.

A low rack is almost on par with having nothing at all between your speakers.  A tall rack is not good and will affect the center image.  It acts like a magnet and also makes the image taller or enlongated, limiting most of the soundstage to the center.

Anything below your tweeters and even with or below you midrange is best.  I also believe in diffusion on the front wall.  I have tried it both ways and prefer the low rack to long interconnects.

George, it is about preference also.  I do not like an image and soundstage that deep with my system.  I prefer layers just behind the plane of the speakers up to 10 ft and in some cases with some layering in front of the plane at the same time.  More of a 10th row perspective.

Most do not have the endless options to experiment with placement.  Some basics to work on in any room:

No equipment rack at the first reflection point on the side

No equipment rack in corners of the room

Equal distance from the sidewall on both speakers

No rack between the speakers (a luxury for most) or almost as good - low, beneath the tweeters and equal or less to the MR.

Diffusion at first reflection point or absorption - smaller room should use absorption.

These basics have worked for me in several rooms I have had some small and some large, but all challenging.

Cheers!