The process of overcoming our defilements goes in conjunction with gaining higher levels of realization.  In fact, when we speak of gaining higher levels of realization in Buddhism we are speaking primarily of the process through which our wisdom and insight deepen.  It is actually the wisdom aspect that enables the practitioner to move from one level to the next on the path.

The attainment of the levels of the path is explain in condensed from in the Heart Sutra, where we find the mantra tadyatha om gate gate paragate parasamgate bodhi svaha.
Tadyatha means It is thus; gate gate means go, go; paragate means go beyond and transcend; parasamgate means go utterly beyond, go thoroughly beyond; and bodhi svaha means firmly rooted in enlightenment.

--from Lighting The Way, by The Dalai Lama