Easiest way to improve the audio on the base stereo?

[RJNavarrete]

My Rebel unfortunately didn't come with the premium sound package, and I'm really missing the harman kardon sound quality from my last BMW. Note: I have the 12" screen, but not the upgraded stereo package, if that makes any difference.

What are some cost-effective, minimally intrusive upgrades I can make to bring this sound quality up?

 

[Moparian]

Infinity 3032cfx for the dash. easy upgrade and if you get them from Crutchfield they come with the adapters. Made a huge improvement in the sound.