I installed a subwoofer under the passenger side rear seat and it really helps out the bass in the truck. Now I’m considering speaker upgrades. What kind of improvements can I expect to see if I install aftermarket speakers in the doors without adding an amp?

 

https://www.f150forum.com/search.php?searchid=19455116

 

If you are not going with an amp for the door speakers, look at speakers that have a high sensitivity. They will play louder with less wattage from the stock head unit. To do it right I would suggest a modest amp around 50 watts per channel. There are some listed that will fit behind the dash so it can be tied right back into the stock wiring. Defiantly look at getting a ck11 harness if you didn't get one already when you added you sub. It will allow you to plug into the stock wiring without cutting into the stock harness.

 

I have a full kicker system but there are definitely better systems out there but the price to sound difference wasn't worth it to me. I got a 400w amp running a single 10 with a sub and then kicker door speakers not hooked up to the amp. Go on crutchfiled.com they let you do sound tests with headphones in. They are really accurate.