Rush's first three Albums really hit the spot for me. Their first, self-titled, album was with the drummer John Rutsey.
I feel it is a must in that it REALLY shows the difference between a band with an "okay" drummer (John) and a Great drummer (Neil Peart, may he rest in peace.)
These three are often overlooked, as Rush only got noticed by the world-wide music scene when 2112 was released.