C4 door speaker upgrade
 

Finally decided to trash the BOSE speakers in my 86.
Already replaced the head unit and bought speaker adapters for the front and rear of the car.
I was wondering to anyone that has put 6.5" speakers in the doors. Is there anything special I should know? Are there any depth issues?
I was looking at Polk Audio db651 for the fronts and rears.
They also make a db651s which is for shallow mount. The difference as I can see is that the tweeter is adjustable in the db651 but not the 651s. That could be huge since you can move it to increase the direction of the highs. I also worry about being able to use the stock speaker grills to complete the look.
Any thoughts would be appreciated.