06 Lux II stereo

I have been disappointed with the audio quality and relative power output of the stock stereo in my '06 Lux II. Can the caddy be retrofited with a factory in-dash unit that improves on this? I am sure that better speakers might help but I think this has more to do with weak power output as much as anything else. I traded a 99 Park Ave that had a FAR superior sounding in-dash system. Would have paid more attention when selecting this Caddy had I imagined that the Lux II stereo was so weak. I am sure that their are after-market solutions but I want to stay with stock/factory appearance on the dash. Any suggestions?