Tried 2 pairs of speakers for 2 channel?

Has anyone tried (sucessfully or not) using 2 pairs of main speakers for a 2 channel setup? I am talking pairs of identical speakers, powered by 2 identical amps. Any recommendations on placement would be helpful.
In the mid 1970's I used what was the a very popular speaker
set-up..called "double Advents". You set one large Advent
on top of the other..with the top one
tweeters together. This was the beginning of the high-end
journey for many of us. I have not heard or seen much about
doubles since...but many current high-end cone speakers
systems...(Wilson and many more) appear to be doubles within
one model/design.
I bought four AR LST's (later called Cello Amati's)for a quad set-up in about 1970. When quad died, I went back to two channel and stacked them. I did not invert either of them.
Later Mark Levinson did the same and even made a custom granite stand (for $8000) bringing the total cost of the set-up to $28,000. He also did not invert them.
Hope this helps.
My speakers are not stackable (for one thing the resulting stack would be 10 feet tall), would a side by side arrangment work? If I made sure the front face was on the same plane for each "set" I am also wondering what problems might arise if I tried to spread them out a bit either on the same plane or all angled in to the main listening area. It is interesting to know that some high end manufacturers have experimented with the 2 pairs of speakers arrangment. I know if a person was to start over spending twice as much on just one pair is probably the best way to go, but if you like what you have and just want *more* of it......
You are on the right track for two pair. Stack them verticle. Take a look at Duntech, Dunlavy, or Montana. don't forget to reverse you speaker cables on one pair so they will be in phase.

Let us here how you make out.

Good Luck,
The speakers mentioned above, Duntech, Montana..etc. have
the woofers farther apart..and the tweeter(s) centered.
The lower the freq./Hz./CPS the more omni-directional, and
the longer the wavelength. The distance the woofers are
apart has a greater chance of cancelling or re-inforcing
the range they cover..on the other hand, the higher the
freq. the more directional or cardioid the pattern of
radiation is. Placing the speakers side-by-side or one
in front of the other has a less likely chance of being of
any merit.