On my 2016 SHO with the sony stereo it came with 2 6x9's and a single smaller maybe 5x7 speaker in the center of the rear deck. I have replaced the 6x9s in the rear deck and unplugged the 5x7. I also replaced all 4 door speakers as well and put a sub in the trunk.
I removed all the carpeting from the trunk and put a sound dampening material from knukonceptz everywhere in the trunk. I covered the bottom of the rear deck in sound dampener as well and have not had any rattling. The only rattling I had to fix was oddly enough the front dome lights, I played around with some paper shims in there until the rattle stopped.
The problem I have with the sound dampening on the underside of the rear deck is that it keeps falling and sagging the carpet down. I cleaned the metal with rubbing alcohol, warmed the adhesive with a heat gun, and it still wont stay stuck. I plan on putting that sound dampening material on the top side of the rear deck instead now.
On the plus side the electrical system on the taurus is quite strong. I've installed "the big 3" and an odyssey extreme battery and 0 guage wiring to the trunk and never experience any light dimming with the 1200 watt rms sub amp and the speaker amp.
While messing with the carpeting on top of the rear deck and installing the new speakers I messed up the alignment for the opening of the rear sunshade and it doesn't like to go up on its own reliably now.