I had Quads, I got rid of them because:
79dB sensitivity.
Very limited dynamic range, can't play symphonies.
Limited LF extension
Arcing.
Severe capacitive loading needs a very well designed amp.
Plasticky tonal coloration in treble.
Sounded best 8 feet out from the wall, net WAF negative
Made in China.
Too many $$ speakers in the house at that time.
Some asshole journalist once wrote that Quads are for grown ups. Maybe that's because all they can play is Lawrence Welk.
I liked them because:
Decent tone overall, especially low mids that would otherwise make a box resonate.
Gentle, natural presentation of music as whole - low phase error.
Excellent wide, 3D imaging
Nearfield listening immersive
Excellent acoustic interaction with my room, due to dipole radiation and limited LF extension.
Bought them used very cheap, sold them fast and easy.