@JayRay has just a Stealthbox & amp on the stock HK system if recall correctly. I’m sure plenty of others have as well. I don’t think it will overpower everything if set to a reasonable level. At full tilt it sure could though.
If you put a little forethought into how you set things up you can add a main amp down the road pretty easily. Have it staged to mount on the driver’s side back wall. That way you’ll only have to pull the smaller back seat out for access at a later date. Also pre-run some Speedwire from back there to the general area under the driver’s seat.