I had a stereo setup in my office back at my old place and had them probably 3-4 feet apart on the desk. I didn't notice much of a difference with that setup. It was definitely louder, but I wouldn't say any better, probably because they were so close together. In my new house I only have one in the office and it is plenty. I do have a stereo setup in the kitchen because of how long it is, not a big kitchen, but its kinda long and skinny. I think the stereo pair in there is really nice because I have much more of a gap between them.
I think it really all just depends on the setup.