I think the easiest answer is to just observe that everyone, to my knowledge, is now recording and distributing stereo samples. If it didn't make an enormous difference then someone would be selling monophonic samples.
Do you have a switch in your current setup that allows you to switch to mono and back to stereo? That's another way to hear just how big a difference this makes. With my current 6 channel setup the change to mono just sucks the life out of the sound. By comparison, the difference between normal stereo and the various audio cycling algorithms (with all speakers in use for both cases) is subtle by comparison.
We did a demo with only three stereo pairs for a job which will presumably end up with double that number. I'm already wondering if it will be more important to get the extra channels or to double up speakers on channels. This is for one particular case where Behringer 3031A monitors are getting driven hard, and while they are still sounding wonderful we may need the extra power more than the channel diversity. Just my thoughts based on what I've listened to primarily with PA systems though with a couple of organ installs as well.
EDIT: Of course it's easy enough to try both approaches and see what sounds best. I'm convinced in this case, but if we all agreed about audio configurations we wouldn't have much to talk about.