As the well-groomed members of the new K-pop supergroup, SuperM, gather in a Los Angeles conference room, they feel as though they've left something on the table. Two days earlier, the seven-piece unit had shut down an intersection in Hollywood and made their live debut in front of more than 5,000 frenzied fans, some of whom had lined up for days just to get a prime spot to see the guys perform. The group was formed by members of four established K-pop boy bands. After months of keeping their identity a secret, the boy band SuperM eventually made their public…