3 feet high and rising is an all time classic. so that is a definite.
De La Soul is Dead. Definitely
Buhloone Mindstate. Not too sure about that one. A lot of critics call it an extremely influetnial hip op album, but that is the one I listen to the least.
Stakes is High. Absolutely.
AOI 1- If they have it, then definitely
AOI2- Not as good as AOI 1
The Grind Date- A good album. I would download it if I were you.
It looks as if they don't have the deluxe version of 3 feet high and rising, which has about 6 or 7 other songs, including the "Buddy" Remix that has Monie Love and Queen Latifah (Largely credited as the first official remix song in Hip Hop), nor do they have the expanded version of De La Soul is dead, which has an additional 4 songs on it.
I would check that Hip Hop Forum Site to see if they have those versions.
They don't have "R U In?" Either. That was a project released in conjunction with the Nike+ Original Run series. That one is really good. Its a continuous track that lasts around 45 minutes. It was created for what else, running.