Just trying to let you know that if you want your amps to run cool and get the current they need I would personnally run another 4 gauge wire or run a 2 gauge instead of the two 4's. Wal-Mart of all places sells an actually decent 4 gauge kit for under $30 compared to the overpriced kits at any other major electronics store. But if you want it how you had it before than by all means just run the one and split it to both amps.

I would still replace your ground wire connecting your negative battery post and chassis. It is only a foot or so and your car's electrical system will thank you.