I have 690's in the rear of my girls civic. If you wanted to fit 690's in the back of the Z, I am VERY sure it is possible.. but would require some crazy fabbing. If 570's fit in the stock enclosure (with some fabbing of course) I would think you could futher mod it for the bigger speakers... 690's own. Perhaps I will try to fit one some day. When I have more money to spend on that kinda stuff :) AGAIN ... There is MORE than enough room for the VR 690's back there, fitting em in requires work and I would be more than willing to make it work... would you be?