421-444

and

448-514

Some key issues in here include:

450-451: the first appearances of X-23

462-468: The House of M / Decimation storyline

475-486: "Rise and Fall of the Shi'ar Empire" written by Ed Brubaker and Art by Billy Tan (This is an AMAZING arc with fantastic art)

488-494: Endangered Species and Messiah Complex tie-ins

500: X-men established in San Francisco.  Magneto is back (again)

These runs have some of the BEST X-Men writers ever:  Chris Claremont, Matt Fraction, Ed Brubaker, as well as fantastic artists: Salvador Larocca, Alan Davis, Chris Bachalo and Billy Tan. 

All the issues were read once and then stored in a comic box ever since.  They have the normal wear you'd expect from being in a box for 15-20 years.  At a minimum, they are in "good" condition, with several having some minor tears in the spine.   Many are in very good condition.