Aftermarket will, but to get better sound you're gonna have to pay a bit of cash...and if you don't crank stereo it may not be much greater sound but a lot more cash. I have a newish car and I don't crank stereo either but I find I could do with a bit of bass (I'm not a bass-child who pumps it driving down road at 20), so for that just an amplifier and a sub in the trunk would do it.
I've always found that stock stereos in cars were quite adequate for treble much of the time, and bass was always the weak point.
BiB