i'd take "paul's boutique" before "check your head", although they're both indispensible
some other random rec's:
a tribe called quest - anthology
-- good starter album for tribe
black star
-- one of the best hip-hop albums of all time
cee-lo green is the soul machine
-- great genre-busting "urban" music
common, "like water for chocolate"
deltron 3030, "deltron 3030"
-- very not-wack "indie" hip-hop
little brother, "the listening"
OUTKAST, "ATLiens"
-- will always be my favorite hip-hop album, great end-to-end
people under the stairs, "question in the form of an answer"
the roots, "things fall apart"
-- simply incredible
talib kweli & hi-tek, "reflection eternal"
-- wow
anything by MF doom/viktor vaughn/madvillain/king geedorah
-- more not-wack indie
nas, "it was written"
-- nothing can hold a candle to illmatic, but i like nas, even his cheesy stuff, and this is my 2nd fav album
2pac, "all eyez on me"
-- everyone needs to own this album
dre, "the chronic"
-- see above
gza, "liquid swords"
-- whenever i hear the opening intro, its hard to turn this album off
method man, "Tical"
mobb deep, "hell on earth"
biggie, "ready to die"
-- see 2pac and dre
snoop, "doggystyle"
-- you have nas, but you don't have this??
wu-tang, "enter the wu-tang"
-- must-have