So out of curiosity, I measured the resistance of my X-LS and my Acoustic Research bookshelves to see the difference.
X-LS: 7.3 Ohms
Acoustic Research: 3.8 Ohms
This really surprised me, because I assumed the brick and mortar cheap speakers would be 8 ohm speakers. Now I'm wondering if the difference has anything to do with why I need more power to drive the X-LS speakers for the same relative dB.