I just finished up my build. I have the 8.4a but no alpine system. I ended up doing the JL Audio CleanSweep to clean up the signal, then did an Alpind PDX V9 which gets me 100x4 for the door speakers and 500x1 for the sub.
I have a JL 10w3v3 in a sealed box under the rear passenger seat firing up and did the type R Alpine 6x9 in the front and a set of Mephis Audio 6x9 in the rear I had from my previous truck.
The system sounds amazing, plenty of volume, way more than stock. I definitely need to do some sound deadening now. The subwoofer sounds great too. I have a bit of a bass craving in me but I don't want to do a second sub since I love my under seat storage at least on one side for all my tools since I use the truck daily for work. It's definitely plenty but I may want a touch more in the future so may consider upgrading to a 12" w3.