I will be finishing mine up shortly. I am waiting on some rca adapters. I upgraded the 6x9 door speakers, mounted in to the factory mounting rings, to better quality full range speakers (not 2 way), added a surface mount 3” balanced mode radiator above the speaker grill and slightly forward of the door lock switch and a better quality silk dome tweeter but you could run the stock tweeter. I built my own 1st order Butterworth passive crossovers with crossover points of 975 and 7800 hZ. Added to this is a Blaupunkt compact subwoofer mounted under the passenger’s seat. This is all run by a Pioneer GM-D1004 amp with an LOC and run with the 80hZ LPF on. The interesting point of my install is there are only two channels out of the head unit so I had to wire the LOC for the sub from the outlet side of the amp. Not ideal but it sounds really good with just three adjustments available in the head unit. The final upgrade will occur when the RCA adapters show up next week. I will be adding an Audio Controls LCQ1. This is a combination LOC/equalizer that will allow me more adjustability than the headunit. It will also clean up the wiring since I will not have the LOC and RCA patch cables tucked in behind the bottom of the center stack. The LCQ1 and sub volume control will be mounted in the storage area below the center seat. If you want more info PM me and maybe I can help you spend your money wisely since I am second time arounding some of this but now know how to make it work first shot. Your 18 should be wired and programmed like my 17. You will have to know how to solder and insulate to modify the plugnplay harness I started with.
The reason I took this approach was I talked to my local dealer and one in Knoxville and neither showed any interest in turning on the rear channels. When you only have 2 channels out you sometimes have to get creative.

Mine is now finished. The LCQ1 is in and the rebuilt/modified harness is complete. I am very satisfied with the sound but need a road trip to dial the EQ in. The RC trucks seem to like the EQ settings to be down from center so it may take a while to get to the final settings. The 5 EQ adjustments to the sub are throwing me a bit of a curveball because I am used to setting only the gain, low pass filter, phase and volume. To actually be able to tailor the sub is interesting to say the least. The total cost exceeded my original budget but that is not abnormal when dialing in a new vehicle. I ended up at about $750.00 in large parts, $25 or $30 in wire and rcas, another $30 or so in misc parts from the leftover and connector bins and about 30 hours for the multiple installs. The nice thing about my finished install is that I can unplug everything and reconnect stock because not one wire on the vehicle has been touched. I even reused the factory 6x9 mounting ring with connector to mount my new 6x9s.

Downloaded a free RTA app on to my iPad yesterday and set up my system this morning. I have a set of B&O S60 speakers, still considered one of the most accurate, in my shop and I tested them prior to setting up my F150. The B&Os have a RMS curve that almost matches the IASCA curve for competition auto sound systems. I set up my truck system using the same music samples as closely as I could to the B&Os RMS curve and only ended up with a slight hole around 320 hZ. The S60’s peak curve almost perfectly mirrors the RMS curve but the truck environment will not allow this to happen. As I test drove the truck the road noise occurs below 500hZ so I needed to boost the sub output and 2 other of the lower registers to offset road noise. I am now done and very happy with the end result. When setting up the sound on your system a RMS app really helps. I have a pink noise cd coming and I will recheck settings while playing it to see if anything needs to change.