Good carpets will become hard to find soon, so we need alternatives.
I went ahead and ordered some samples in summer.
There is two different kinds: Cutpile and Essex. Cutpile is a thin material, while Essex is "plush".
Both of them can be had with or without sound insulation backing.

Essex Vs. Cutpile


Samples over factory tan carpet.
After reviewing the samples and some online research I decided to go with the thicker Essex material.
Also, I wanted to go a little darker than the faded factory "anthrazite", so my color of choice was Dark slate.
ACC quoted me $556.20 without the backing and $711.94 with the backing.
Rockauto is $249.79 and $319.79 for the same thing.
Basically the response I got from ACC is that they are not setup for retail sales and can't match the Rockauto price.
I decided to go with the backing, since I found reports online that said the fit would be nicer with.
The carpet comes without any of the cutouts. You will have to copy those over from your old carpet.
The cheap plastic foot bolster will have to go before I install the carpet. I will most likely have the upholstery shop cut a piece in the factory shape and size and sew it in.
Here is some detail pictures:





The sample piece is from a 535 with anthrazite carpet. So if you want to match that you will need the 1097A Charcoal
Next step: Testfitting. I should be able to do that in the next two weeks.