While they aren't 6x9 speakers and since there is "no window" to post about car audio on Audiogon, I will offer my favorite from many moons ago.
I loved my Acoustic Research AR2's (set into the parcel well, removing the package shelf) wired into my Realistic under dash cassette deck in my '74 Volkswagen Bug. Riding along listening to Dire Straits and Boston sure seemed to work fine LOL. I haven't installed an after market stereo in a car since the 1980's unless you count a vintage car acquisition here and there. OEM does fine.