If you liked the Main Ingredient, you should peep Mecca and the Soul Brother. I figure most people who care enough about rap music to talk about it with strangers on the Internet have heard "Straighten it Out" and "T.R.O.Y." already but there are other gems. Since you liked KRS-One, I'd check Return of the Boom Bap, too--plenty of DJ Premier beats and KRS at his best before he went off the deep end.
From the 2000s, off the list in the original post, the albums I *love* or used-to-love-than-excessively-played-and-got-sick-of-em are:
(ranked in descending order of virgin-ear-friendliness)
The Blueprint
Hell Hath No Fury
A Piece of Strange (I might be wrong about where I ranked this considering the album's inexplicable obscurity. I blame it on the group's stupid name.)
Supreme Clientele
Masters of the Universe
Deltron 3030
Madvillainy
The Cold Vein
Beauty and the Beat
I'll Sleep When You're Dead