I would install the amp first. I have the kicker upgrade speakers on all four speakers, with PBR300x4 amp. I'm total impressed with this setup, much more than I could have ever imagined.
2014 XC Titanium, VM1-DR Cams, PC5, 1/4 turn, PTS, Hi flow filter (Vic Shop), tri-ovals, Tour pack, PBR300x4, W/D amp bracket, v-twin audio wiring, (4) kicker premium speakers, laydown plate, Bag fillers (Vic Baggers). Dyno: 121.44 HP 116.83 Torque