I'm replacing my Trailblazer's (w/o bose) speakers while retaining the factory unit/amplifier. The front speakers are 4 ohms, which is just fine, as all aftermarket car speakers are. Trouble comes when you get to the rear speakers - they are 8 ohms. Would it hurt the amplifier by switching to 4 ohms? Or could it make it get too hot? Please help me.