How to upgrade my 2017 Ford Focus SE sound system?

I'm wondering if there's an amp already in the unit somewhere so I can potentially hook a subwoofer up to it.
I'm a skilled craftsmen and I'm planning on making a bandpass sub box. I'm aware that the amp that s possibly installed won't produce an impressive amount of watts but if I keep the factory speakers and make a bandpass sub box I should be able to use the remander of the watts to get a decent sub, right? I also want to plan for when the speakers go out, so is buying a new amp the best option? I also need advise on what sub to get and how to take off the front panels properly

Some of the new focuses have a 390 watt amp that's not enough power to make putting a big subwoofer in it you can hook one decent 10 inch to it if you want to under power all the stock speakers in the car. My 12s can't even take less then 500 watts it's really not worth hooking up a sub your stock speakers are going to sound better and probably bump just as hard

Go to crutchfield.com
when you put in your vehicle information they match what will fit along with what is needed to make it work. All the wiring and sometimes the extras are included for free.

"if I keep the factory speakers and make a bandpass sub box I should be able to use the remander of the watts to get a decent sub, right? "

Wrong. It does not have a separate amplifier and one isn't offered as an option because there's no factory option for a premium sound system. All 2017 SE's have the standard non-amplified audio system with cheap, low power speakers and a head unit that doesn't have a powerful channel that can be dedicated to running a subwoofer. Therefore buying an amplifier is your only option. If you want one that can run a sub and all the speakers you had better plan on upgrading the speakers at the same time because the factory speakers can't handle any more power than the head unit puts out (about 15 watts rms per channel x 4 channels).