Audio problems in 2004 Prius

On the tail end of our most recent road trip, the sound system in our 2004 Prius went wonky. Probably a bad speaker in the front left door (though my husband fears it might be the amp). Symptom is a boom, boom, boom any time unless the bass is way down or the balance is to the back.
So two questions for this very smart crowd:
Any thoughts on whether it’s just the speaker, or do we need to replace the whole system?
Has anyone had problems changing out speakers? There’s also concern that the door is never the same once the inside panel is removed to replace them.

I have no idea whether the noise might be caused by a bad speaker or the radio amp. But for the mechanically inclined the Prius door panel is fairly easy to remove. Remove the triangular trim piece at the front of the window by giving it a quick outward jerk. Remove the phillips screw from the pull handle in the armrest. With a small screwdriver unclip the trim piece beneath the inside door handle to find and remove another phillips screw. At the middle bottom of the door is a recess you can use to give the door panel a quick jerk to loosen the retainers around the bottom. Continue pulling around the perimeter of the panel until it is off. The speaker is riveted in.

From the trouble you describe it sounds like there is a problem with an amplifier stage. Some DC voltage might be getting through where it shouldn’t be. I don’t know if your car has a seperate amplifier for the speakers or not but I would assume it doesn’t which would mean the trouble is inside the radio istelf. You can get used radios pretty cheap from Ebay or salvage yards. I suggest you try that first before digging into the door. Some of them for sale are around 70 dollars.

I would check the speakers buy taking the one that’s acting up and hooking it up on the good side.

It would be a lot easier to replace speakers than the receiver. You might see if there are instructions in a Haynes manual: