I had mb quart premium component 6.5 in my doors with eclipse 4 and tweets in the kicks in my old contour. That was the best sounding system I've had. I now have mb quart comp 6.5s and tweets in the kicks and it sounds great, but not as good as my old setup. The midbass from both setups is more than enough, but the eights would give you something extra: up front sub-bass. If you are willing to do it, I'd go for the eights give them 40hz and up. This would probably score you higher in the sq department at the competitions.
