Check out my sound system build for some details that may help you decide how to proceed.
You can replace speakers and it can help a bit but it will not solve the real issues. Bose sends way too much sound to the front dash mid speakers (centerpoint). They are small mid range and do not give a good full cab filling surround sound many of us prefer.
The Bose signal to the rear doors is almost non existent. Stock speakers are 3 ohm. I replaced with infinity 2.7 ohm and 92 db sensitivity speakers, those are really good specs for a speaker that can produce good sound with low power needed. You can buy $1,000 speakers down to 2 ohm but that 2 vs 2.7 ohm difference is pretty negligible to what you would hear.
Swapping dash and front door speakers will help some, but waste of money for rear door. Signal is just not there.
That leaves you with getting a digital sound processor and amp, or amp with DSP to correct the input signals to give you a full signal to all speakers you can tune appropriately.
Good news is you can do this pretty cheap. About 300 for speakers in my case and around $250 for the JBL 8 channel amp with DSP. Now you have a good signal, with way more power to each speaker which are better quality.
That takes you to bass. If you want more then you need a sub. You can do the factory kicker option, but I feel that is over priced for what it is.
A simple 8” or 10” sub designed for a small box, in the enclosure of your choice along with an amp will take care of the bass side of things. I used a kicker amp that puts out 500w at 1 ohm ( probably 3 time more than the factory aftermarket option) and it corrects the drop off of bass frequency the factory system does. Bose set up cuts down bass the higher you turn up the volume to prevent the crappy speakers from falling apart. You need an amp that corrects that drop off from the factory input signal. The kicker amps with Key running do that.
I used my 8” sub box from my old 2007 F150, put in a pioneer dual voice coil sub and packed the box with Polly fill. I added a bass knob to the dash so I can turn the sub up and down to match what I am listening to.
So that was about $150 for the sub and about $200 for the amp, box I already had but you could make one yourself that would only take up 50% of back under seat storage area. So bass for $350 plus box vs factory option which is about $1000.
My bass shakes the whole truck, side mirrors and will vibrate the rear view to the point I can see out of it. I never turn it up past 50%. You will not get that kind of power out of the factory version, but it will add bass for sure.
No right or wrong way to do it, just got to decide what you want to take on yourself, how much you want to spend, and how much better do you really want it.
I like to do things myself, with the best result possible, at a price lower than off the shelf solutions so that impacts my choices.
