The linked rendering of a stretched SRT-6 with a rear door seems to be as old as the internetz. That said, I have always thought of this graphic artists concept as a winning idea. I would have been seriously interested in this car if it was ever made. Now there are plenty of 4 door coupes as another poster said - think Porsche Panamera. This concept the OP posted, while interesting, has lost the lines of the Crossfire - probably to make a more practical 4 seater (widened the body and beefed up the outer sheet metal).

http://www.cwwcardesign.com/cars/pic...rcrossfire.jpg