I just added a 10" sub to mine. I'm running a set of Pioneer coaxials up front with the factory tweeters still connected, and the factory speakers in the rear door.
I put the amp under the driver's seat, so if I need to pull the sub box out for cargo space it's just the speaker wires on quick connect terminals. If you have the rear heat option, forget about using space under the passenger seat. There's a fan under there.
Here's the amp, sub and box that I'm using. It's budget setup, but it really sounds pretty good.
Rockford Fosgate R250X1 Prime 1-Channel Mono Block Amplifier - $101
Amazon.com: Rockford Fosgate R250X1 Prime 1-Channel Mono Block Amplifier: Car Electronics
Scosche SE10R 10-Inch Subwoofer Enclosure - $27
Amazon.com : Scosche SE10R 10-Inch Subwoofer Enclosure : Subwoofer Cabinets : Car Electronics
Infinity Reference 1062w 10-Inch Subwoofer (Dual Voice Coil) $59.95
Amazon.com : Infinity Reference 1062w 10-Inch 1, 100-Watt High-Performance Subwoofer (Dual Voice Coil) : Vehicle Subwoofers : Car Electronics
For under $200 including power wiring and fuse, the truck now bumps pretty good when I want it to. My next step will probably be adding the Alpine amp for the front and passenger speakers, and upgrading those. The sub will make more difference in the sound quality than just the bass, because you take that load off your front amp and speakers and move it to something designed to handle it. :boink: