Line-X and the other true bed-liner products are indeed durable, and if properly applied, probably the closest thing you can get to indestructible. However, you might find the texture too rough and aggressive for a speaker cab as applied by most truck-bed-type guys, and finding a vendor willing to experiment with dialing back the texture could be a bit of a challenge.
While not nearly as durable as a 2-part, catalyzed coating like bed-liner, DuraTex works well enough for DIY purposes. IME, you need to apply two full coats before doing the texture coat to get it on thick enough to last.
Carpet, as @agedhorse sagely pointed out on the first page, is available in widely varying quality. The original Ozite-based stuff, as used by the SR industry, is incredibly durable, but I'm not certain that product is still available. Although I don't care for it personally, I get why some pro sound companies went that route...I have some 20(+)-year-old Showco boxes sitting in my shop right now and they don't look all that bad, given the number of miles and shows they've probably endured. But the carpet covering on them is infinitely superior to the covering on all the manufactured MI products I've ever seen, some of which are little better than felt, IMO. The term 'rat fur' (around my shop we called it 'monkey fur') is used to distinguish these inferior products from the real stuff, and it is indeed derisive. It's intended to be.