Could I ask you all for some suggestions?

I've dabbled in K-Pop before, and I'm itching for more.
I was lead to Reboot and 4 Walls last year because of their acclaim, and I found out about Why So Lonely a few days ago. I really love all 3 a lot.

Those are the only albums I have in my iTunes, but I've vibed with everything I've seen on YouTube (Girls Generation, 2NE1, Orange Caramel, Red Velvet). Are there any albums that are considered "required listening" that I should tackle first?