4 Amex cards at once are probably too much for 1 person.
You might want only 2 Amex cards, and then other cards from banks such as:
Chase has 70K bonus Marriott + 1 free night. No spending requirements.
Chase Priority club 80k bonus. Also no spending requirements.
Citi AA Amex 50K
Citi AA Visa 50K, if use 2 browser trick.
Chase also has many other good offers right now.