Just bought a used 2007 RDX Tech, the audio is shot. Sounds like crap and I really don't want to replace with oem speakers. Anyone can guide me to upgrading all these speakers? I know aftermarket stereos are a nightmare for this vehicle, so ideally I'd like to -

1. Keep the factory radio
2. Replace all door speakers (I could care less about the center)
3. Add a Amp+Subwoofer

Is it possible to add 2 Amps? One for voice and one for subs? Looking for the cleanest install, I hate external boxes. If I could install new speakers in the door and have it powered with another amp than the factory that would be great. Please advise.