I don't really care about his origins. They were no more confusing in this movie that Old Spock and Nero's crazy Romulus-destroying Red Matter adventures.
I just wanted to see the Botany Bay.
Honestly, I had seen TWOK many times before I ever saw "The Space Seed," and Khan's origins in that movie were just as confusing. Wait, so you and Chekov know each other? And you're marooned on this planet? But you've been alive since 1996? HUH?!