i've mitsubishi mirage 14 with pioneer avh1300nex head unit

i want to upgrade the front speakers (i didn't decide yet to which)

i dont want to buy an amp

my question is very simple

using aftermarket speakers without external amp can cause a damage to the speakers? or just i don't get the full power of the speakers?

im asking it because on my head unit pdf manual they said up to 50W (see image)

Should be okay, as long as the new speakers have the correct resistance (Ohms).  You will notice a significant improvement over the OEM speakers, if you chose the correct and good speakers.