My guess, and it is a guess only, but odds probably low. This is assuming oem speakers are 4 ohms and wiring another speaker in parallel creates a 2 ohm load. Just about all modern amps can run 2 ohm loads safely. If you look at amp specs on a car audio supplier site and check their cheapest amps, they mostly if not all, are rated at a 2 ohm load. So if the oem speaker impedance assumption is correct and the oem amp is built to at least similar build quality of most modern amps, then should be ok.