Aftermarket stereo receiver

I am new, please go easy if I put this in the wrong section.

I'd like to replace my stock head unit/receiver with something that has an AUX port for my tunes. I know there's a couple forums where people have compiled a list of receivers that keep the same orange color so it doesn't look so out of place with the car BUT that's not what I'm asking for (though if you have a suggestion, do share!)

The '99 m3 vert has a small subwoofer in the back (free baffle). If I buy a receiver, will I need to also buy an amplifier? If not, is 50Wx4 adequate? I just want my aux port and all my speakers + sub to be in use, nothing fancy.

dispense your wisdom upon me.