Why are you looking to replace them? What don't you like? I've got an R172 and the sound is pretty good, once optimised.
Many people don't know what to listen for. I do. Ex national Sound Quality judge (2015ish), I've run a national manufacturer competition team and helped setup cars that have done well internationally (2nd/3rd in Europe)
The speakers aren't amazing, but they're better than most people's. The standard setup in no way optimises them, though. 15 million speakers just makes things worse. I was considering a full replacement, then found out how to enable the fader. Forget the rear speakers.. fade full front, 2-3 steps towards the passenger, and +2-3db treble and +4-5db bass. More speakers isn't the key to success.
Sure, it's possible to do better, but in the stock locations? Even with sound deadening, better speakers and therefore better amps, plus time alignment? The improvements would be minimal
If you swap, you're likely going to add less efficient speakers, which means more amp power.. it's a trouble-fraught route
I've listened to 100s of cars, setup many and i won't be replacing mine unless they're blown.
If you do want improvements and they're not blown? Best improvement will be to add a DSP with time alignment first