There are two main factors that set how easy or difficult a speaker is to drive, these are Speaker Sensitivity and Impedance. A speaker rated lower Ohms requires more current than a higher Ohm speaker. Similarly, a speaker with lower sensitivity requires more power to reach the same volume as a speaker with higher sensitivity.
Klipsch Klipschorn AK7's nominal impedance level is 8 Ohms but can go down to as low as 4 ohms. 8 Ohms is pretty much the standard impedance amongst stereo speakers and amplifiers so Klipsch Heritage Klipschorn AK7 is not considered a difficult to drive speaker from Impedance perspective.
Klipsch Klipschorn AK7 has a sensitivity of 103 dB. 103 dB of Klipsch Heritage Klipschorn AK7 is considered a high sensitivity compared to average stereo speaker which makes AK7 an easy to drive from Sensitivity perspective.
Read our detailed Klipsch Heritage Klipschorn AK7 Review