Does anyone play two pairs of speakers at the same time?

Rather fun to read all the differing viewpoints. I'll admit to stacking some cheap junk in college before my first real stereo. But ever since I have only used one (hopefully well-designed) pair at a time. I think a single high-end pair achieves the most pure and true-to-life sound you can get. (I don't/can't design my own.) A dedicated equal five-channel system is totally different and might be superb, but I've not got the money.

While fiddling with combos of speakers or more might be fun, and the sound pleasing to the listener's ears, I fear it is is in reality atrociously inaccurate. If the listener enjoys it, I'm all for doing it.

But I'll bet the non-casual listener, who enjoys sonic accuracy, would be shocked to hear an acoustically well-set-up quality two channel speaker compared to a mish-mash of various speakers channeled together when volume matched. It's all good; just keep listening!

I've seen people running two pairs of speakers, either from one amp or two amps, and enjoying the fullness of sound.
If it sounds good, why not?
Of course, 'good' depends on the personal taste.
I think some pairs may work, but there's a high chance that the sound gets muddy with interference if not properly set up. With one amp, at least the efficiency should be in similar range.

So I just got another pair of Focal Sopra 3 for another room but decided to try how it would sound to have 2 pairs running side by side in the same room with the same integrated amplifier (Anthem STR). Initially I placed them side by side and the sound was visceral and the dynamics were unbelievable. But the sound stage got muddy. Then I measured the tweeter distance from listening position on both pairs and got them aligned as good as I could so that the upper frequencies would reach my ear at the same time. The sound stage got much better and all the qualities of running both pairs at the same time were still intact. I must saw I am in complete awe. The sound is so much more enveloping, real, effortless. The bass is more even and full. I also got rid of some of the peaks from the standing waves, which could be a result of having both pairs in slightly different locations in the room. Absolutely Loving it. Now I’m not sure if want to take one of the pairs to the other room and just want to leave them both side by side. Will play with placement to get it aligned even better to get the sound stage to be as good as playing the single pair, if that is even possible. 
Having a lot of fun with this! 

Great! In the past I have only done large Advents stacked and some smaller stand mounts, also tweeter to tweeter. Now I'm playing my highly modified Klipsch Quartets and RF 3 lll together and enjoying the sound.

Bilaltata,  you will see on the first page of this thread the success I had (and still have) running Focal Utopias and Focal Electra 1038BE2’s together.  What I’ve  done since then to make them even better in performing as a pair is muting the tweeters on the Electra 1038 BE’s.  Two pairs of tweeters can compete with each other and creat comb filtering.  If you mute one pair, you may find the imaging and overall sound is even better, beating what you have already achieved.