A single 4 gauge wire is plenty for multiple amps. I have two amps running over 1200 watts on four gauge with no problems. Also running two wires to the trunk isn't less of a hassle it is more! Thirdly there is a reason that people use distribution blocks...for wiring multiple amps and protecting them with additional fuses. Besides a distribution block jutifies itself when two fuse holders near the battery are close to the same price but lack that extra protection that a distribution block offers
