Rb Wolbe complained about the yungerleit in the Mir learning kabbalah. He said - If you don't understand Mesillas Yesharim, then don't learn kabbalah, and proceeded to give four examples of how the Mesillas Yesharim can be understood al pi kabbalah.
See also Rb Wolbe's non-haskamah to Patterns in Time (Chanukah).
I think his point was (and I think Rav Hirsch made the same point) that you can learn technical kabbalah and know how all the words fit together, and it will mean astoundingly nothing if you do not understand the reality it represents.
Or in other words, if you don't understand the amkus of the aggadatah in Shas (nod to @DoubleAA above) or even Medrash Rabbah, then why would you bother learning kabbalah.
On this note, probably a good entry to understanding these sources at a more profound level are Pachad Yitzchak and Maharal.
After that I would probably recommend the writings of Reb Yitzchak Eizik Chaver such as Pischei Shearim (intended as an introduction to kabbalah) and his commentary on the Maalas Hatorah.