I've dryhopped with Willamette and Cascade together once (1:1 ratio Willamette/Cascade). I wasn't a huge fan. The Cascade overpowered the Willamette for sure, leaving my nose and taste buds with mostly the intense grapefruit (or cat pee, as some prefer) of the Cascade. Now, Cascade and Amarillo together... that's what I'm talking about (and also what I'm drinking right now)! This combo works much better together IMHO, as the Amarillo adds a lot more citrus complexity to the Cascade flavor/aroma.