93 Century Speaker Help

Hey all, just got a very clean 93 Buick Century and I'm looking to drop in some new speakers all around. I'm looking at either the Infinity Kappa series or Polk Momo's. My question is about the 6x9's in the rear deck. Did anyone have any problems with just dropping a new set in the metal brackets to mount them from inside the trunk?

I was looking at this today and with these speakers (both 3 ways) they have tweeters above the woofer, and I was wondering if this would not fit underneath the rear deck panel?

I was thinking maybe cutting out the holes in the rear deck and mounting them from inside the car would be the best option? But was just wondering if anyone had a similar experience with this and what you might have done?

Thanks!