[LAU] more than 4 channels for listening? Really?

Folks, I'm an audio lover that prefers smaller speakers in smaller spaces and i don't need/want 5-8 speakers in my listening space. I have found that i prefer the effect of vocals/sound effects that are mixed in center in stereo speakers, over a center channel. It sounds more natural and rounded to me. I would think that the same thing could be done in the rear speakers of course and also front to back by adjusting the front-back balance of sounds. Couldn't one create the sound of a fly moving through out a room simply by adjusting the balance of 4 speakers? If so why do we need more than 4 speakers? I have an audio system for which i'd like to set up 4 channels. I have 2 Anthony Gallo Acoustic Reference 3.1s and would like to swap them out for 4 Stradas and 4 subs (with some extra money of course). If i do that and play back a 5.1 or 7.1 movie soundtrack or music disc what am i going to not have vs a full 5 or 7 channel set up? Will things down-mix properly (using pulse audio for reference)? Bearcat M. Sandor