04 Cavalier Stereo 4-ohm compatible?

I have a 2004 Cavalier with the factory head unit with CD player. I want to change out all the 10 ohm (!) Delco speakers but am concerned that aftermarket speakers might harm the radio. Is the factory system compatible with running four 4-ohm speakers? Why does GM use the absolutely worst paper cone speakers available, and 10 ohm ones at that?

lol, I swapped my blazer speakers out (sounds to be same head unit) from 9.5 ohms in back to the 4 ohm speakers i have now. works good. Odds are it would work, how would best buy and cc stay in buisness if they cant swap speakers in these vehicles.99 Blazer LT.   Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)