Unless you use your third row, I wouldn’t worry about the tiny speakers in the cargo area. If they are bad, just rip them out and don’t replace them. Same for the front speakers at your knee.
The front door speakers can be replaced with 6.5 inch speakers after removing the door cards, which is pretty simple. You will retain the original factory grills.
The rear door speakers can be replaced with 6.5 inch speakers as well, but you will need to mount them directly to the outside without removing the door cards. You will not retain the factory grills, Unless you want to use smaller speakers.
Here is what I did
Bottom left are the speakers mounted in the front doors. Bottom right are the speakers mounted directly through the door card utilizing new grills, which I painted to match.
Also, my factory amp was blown, so I just removed it and everything is being powered by my new head unit. Plenty of power for me, but I’m not 17 years old anymore.