Here's the biggest problem I see right now with car audio. If you're lookng to spend under $10,000 and still have great sound all around, including bass, you're looking at the Alpine MRD-1001 amp (2 of them) or their new f-1001 and 2001, again one per sub. After that you would be looking at the type-x subs. Optimal number or those is 3 10" or 2 12". Now, this is where is gets tricky, I know because I have had to do it. I have two BMW's; a 1996 BMW 318ti and a 1998 BMW M3 convertible. The problem with both is that as it stands right now if a speaker goes, you have to go back to bmw (same thing applies to the g35 and the rest of nissan as well). Now, When the speakers went in the ti, I went to my local custom car audio shop and asked what I could get for my money that would match up perfectly with the stock cutouts. The answer was nothing. The mid-ranges in the doors are 2 1/4" in diameter and the tweeters right above them are 2". No one sells speakers that small in the aftermarket world. With the M3 it's easy because they have the Harmon Kardon System, and since that bodystyle M3 is so very popular, there will be no problem getting speakers for that.
Now, as far as companies go in the car audio arena, these are the only ones that are worth looking at.
Alpine, arguably the best name in the business, a wide variety of products for anything and everything. Greatspeakers, awesome amps, and awesome subs.
JL Audio, not necessarilly the best out there, but those subs rival the ones of Alpine.
There are only two listed. The reason is because the other companies you named (MBQ, Focal, Dynaudio) all use cheap parts so they can sell for cheaper, but their products were never meant to last that long.
Image Dynamics is awesome, but spend $10,000 on a complete system and another $15,000 redesigning the dashboard because of the main horn tweeter, and you understand why it's not practical for everyday people.
Now, Klipsch could go a few different ways with this; they could be aftermarket, they could be a stock company, putting their speakers into cars that go into the showrooms right off the assmebly lines and then create more product for people to buy through dealerships if a speaker ever goes (like Harmon Kardon does), or they could simply do both of those options.
Now Harmon Kardon I believe does not relinquish control over their product to BMW. BMW asks fr certain specs, HK delivers the product to the assembly plant, and its gets put in the cars. HK then makes more product for replacements, which are made with the same HK quality. (not that I am saying that HK stand up to Klipsch, as I would be called a blasphemer).
Now the other problem is that with Alpine, you have to spend over $10,000 just to get your car to sound like your Klipsch home audio through what they call the "F1 Status", in which that strip everything audio out of the car and replace it all with their stuff, which includes and equalizer and is rated for Dolby Digital 5.1 . But with F1 status, you don't do ay of the work, oh no, it actually will not be done if you insist on putting it in yourself, becauase Alpine has made speakers and equipment for F1 that are so expensive, in order to even say the name F1 your store or even advertise it, you have to be authorized to install it and selll it. On top of that it takes about a week for them to do everything because of the long drawn out process it takes of taking out all the stick wire and replcing it with Monster and StreetWire.
Now, here's what I am getting at. Yes, there is not a lot of money to be made in the car audio market as it is now, but if there was a company willing to take a chance and make a product that blows the others away, ad sell it for the same price, if not better price than Alpine and it even destroys Alpine, it would be worth it. Now, obviously, the acoustics within a car are much different than home acoustics and there would be a monetary investment that would have to be put into this, but I believe if Klipsch ever did what just stated above, their profit would be at least 10 fold of their initial investment.