Bringing this back to ask a related question instead of starting a new thread. Forgive me for being a car audio newb...
I understand the dash tweeters and front door woofers work in tandem to provide the front sound. I am looking at replacing speakers only, no additional amp (please not try to convince me to add an amp).
Will replacing the front door woofers with 2-way speakers provide any benefit (would that make 4 tweeters in the front?)? Or would that just negate the dash tweeters? Would this provide better sound quality?

Yes - you would effectively have 4 tweeters in the front of the vehicle if you replaced the door speakers with coax and left the dash speakers stock. Whether this is a benefit or not will come down to your equipment, install and listening preferences. Some people like powerful and sharp "highs" (treble, vocals, etc) in their setups; but more often than not adding redundant high frequency drivers to a system creates nothing but issues.

Theoretically speaking, you would be better off adding a 4ohm 3-4" coaxial (2-way) in the dash and replacing the door speakers with a 2ohm mid-bass/woofer. This will keep the frequencies separated as designed from factory, while adding better response and output.

Thanks for getting back to me!
After doing a little more research (and not hearing back on this thread), I decided to pull the trigger on the OEM Audio + speakers. I found a used set and got a good deal on them. Figured it was the easy solution that is plug and play. They sound better than stock and I think I'm content with the sound for now.

Great call there. OEM+ takes the guesswork out of it and ensures that the proper loads and frequencies are accounted for.

If you don't mind me asking - how much did you scoop the used speakers for? I am in the process of buying the equipment to add DSP/Amp + 3 way front components and Subwoofer, but want to leave the rear speakers running off the HU. I may keep on the lookout to go OEM+ with them if a deal comes around....

cheers

Thanks! I only went with the speaker upgrade because I don't want to loose any storage space in the rear (yes the subs are elegantly integrated but every square inch counts).
I'd say it will be hard to find a used set of OEM Audio + speakers because most will either enjoy them or not bother parting them out when they sell. I was lucky to find someone upgrading the entire audio system to a one-off custom setup and they decided to let go of their speakers.