Trip to Napa / Sonoma--favorite winery?

[RAD]

This message exists in other forms in other threads: Italian wines (barbera) and ports (California ports).

But just to cover our bases:

My wife and I will be in Napa / Sonoma this weekend, 7/8-9. We already have plans to visit a handful of wineries (Matanzas Creek, Fife, Caymus, Jordan).

Does anyone have a "must-see" suggestion? A diamond in the rough? A place with something different and interesting, that is available only at the winery, perhaps?

We definitely have thoughts of our own, and it is short notice, but we're interested in others' opinions!

Thanks!

RAD