Mark,
I agree with the previous suggestions, "Extensions" is great, to me his best single album, and the Impulse's are the period I like best ('Tranquility', 'At The Top: Poinciana Revisited', 'The Awakening', 'Freeflight, 'OutertimeInnerspace'). The last two are from the same 1971 Montreux Festival Concert. The Impulse titles are easy to come by, and most have been two-fer'd.