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


I have found that certain combinations of speaker pairs produce a better sound than the single pair alone. For example: Klipsch Quartets and PSB Image 4T (new tweeters from Vifa) Quartets inside pair and volume matched to PSBs. I have done this over the years and found some great combinations.
aburnhamuu
Man, talk about comb filtering and phase issues! Getting the drivers in one loudspeaker to "speak as one" is hard enough, why make it much, much harder by pairing two different speakers? Very bad idea. There's a kid posting on the Planar Speaker Asylum lately---he is running Maggies and Klipsch (don't recall the model of either), side-by-side and simultaneously. What a mess!
I don't seem to have any serious comb filtering or phase issues. Sounds bloody righteous
If you are not running 2 amps off of your pre,(providing the pre has multiple outputs) isn't the amp seeing potentially damaging low impedance?