My choice would definitely be to rip the factory carpet out, insulate the floor with either dynamat or the duct insulation that people have used, and then put in either
BedRug or
BedTred.
I used the bedtred because its less carpet-y, and love it! It's like bedliner that you can take out anytime you want and put back in. Power-washable, uv resistant, and wipes clean easily also.
Tough stuff!
This pic is from when i had just gotten the back installed (My install job was a bit crappy because of my effed up hands, but it's easy if you have normal hands!)
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