"Yes" is among my top 3 favourite modern bands. They are all fantastic musicians, performers and personalities.
If I may, I would recommend listening to Steven Wilson/Porcupine Tree. If you listen to two albums of each (PT being Wilson's former band) I'm sure you'd fall in love with them, though PT isn't exactly "modern modern".
The "Karnivool" albums, Sound Awake and Asymmetry are both excellent MUST LISTEN albums.
If you're up for the challenge, then I strongly recommend getting into bands like, The Mars Volta and Between The Buried And Me.
I really enjoy Queens of the Stoneage as they are what I believe to be the epitome of a Rock 'n Roll band in the current decade.
If you're into jazz then I have about 100 artists to add to that list, but since you mentioned "rock" bands I gave you my list of musics that I'm never without.
Do with it as you want :)
RE: A Grumpy Old Man in Search of New Music