Car Audio: Appropriate Fuse Size for Dual Amps?

My car’s speakers are currently powered by a four-channel amplifier. I plan to buy a 12-inch subwoofer as well as an amplifier to power it. I’ve run a 4 gauge wire to the trunk for my existing amp. I’ll get a distribution block and connect it using 4 gauge wire, as well as 8 gauge wire from the block to each amp. My question is: how do I determine the fuse size to use? I already have a 60amp fuse for the current amp, and I’m not sure what size fuse I’ll need to replace it with. Do I replace my 60 amp fuse with a 120 amp fuse or leave my 60 amp fuse because the new amp will almost certainly require a 60 amp fuse? I believe I only require a single 60 amp fuse, but I’d like to double-check before purchasing anything. Thanks.