Please help...looking for music advice for 2014 Buick Encore

I'm looking to add sound to this SUV without spending thousands of dollars! The one in it can NOT be replaced because of the small screen on top and other controls including car computer controls. I'm just thinking of something I can put in it so I can use bluetooth and USB for music. I found a AC plug connection (150w max) in the back seat area. I first thought a soundbar and wired sub combo. Wired because of no added radio waves and interference plus no more wattage draw because of a wireless SW, Anyone got any ideas? PS having a hard time finding a wired SW soundbar.