"I have a pretty decent Focal Utopia 3 Ways with Focal Crossblock No 7.
I understand car hifi will never be as good as home hifi but as I travel about 600 miles weekly I am willing to spend at about half the price of the cardas golden reference."
I get the fact that you want good sound in the car, but unless you set your car up with a complete system that will equal something you have in a home, money spent on an expensive cable will be wasted. I know that the acoustics in a car are not very good, but that's not even the real issue. Car audio components, even very good ones, won't sound good enough and have enough resolution, to hear any positive difference an expensive cable will make.
If you don't believe me, its easy enough to test. Go get some car stereo equipment that you can return from a place like Best Buy and a 12v battery charger and put it next to whatever you have in your house. After a few minutes, you'll see that its not worth getting involved with.