Klipsch claims your RF-7 speakers are enormously sensitive at 101 dB (I find that difficult to believe) and are "8 ohm compatible". I'm not at all sure what "8 ohms compatible" means. Is that what their engineers said or is that what their marketing people said?
The measured impedance curve for theses speakers shows that between about 80 Hz and 600 Hz, they go below 8 ohms. And between 100 Hz and 200+ Hz they dip below 4 ohms. Observe the black trace while using the vertical scale on the left side.
So despite what Klipsch claims, these speakers are below 8 ohms over a significant frequency range. When you also consider the green trace (impedance phase angle measured in degrees on the right side), that same frequency range where the impedance dips lowest is accompanied by the largest swing in phase angle. This adds up to mean these speakers are difficult to drive over that frequency range.