One alternative, especially if you have multiple cables to pass through the firewall, is to pick a convenient spot & use a flanged tube, along with intumescent caulk & firesleeve. Spruce sells a kit for a lot of money, or you can search ebay or the local big box store for equivalents (stainless towel rods or grab bars). You can work around the mess of the caulk by 'running some lines' on a non-stick surface, letting them cure, and stuff the empty space in the tube with the little sticks of caulk.
You can even run lines that at a bit antagonistic to each other (noisy stuff with small signal stuff) by having them diverge on both sides of the firewall, so they are effectively crossing in the tube.
Charlie