Until Thanatos and Pluto, your Dark team doesn't really need any upgrades. While SSR Amon is stronger than Satan, Awakened Satan will be stronger than SSR Amon down the line.

We don't know if Thanatos will be available in the next Miracle Ticket or not. She's around the cutting point, so this is an open question and will depend on how Nutaku feels like handling it. As such, your thread is premature. Come back once Miracle Ticket is actually out.