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.
Focal Vestia No4's nominal impedance level is 8 Ohms but can go down to as low as 2.6 ohms. 8 Ohms is pretty much the standard impedance amongst stereo speakers and amplifiers so Focal Vestia No4 is not considered a difficult to drive speaker from Impedance perspective.
Focal Vestia No4 has a sensitivity of 92 dB. 92 dB of Focal Vestia No4 is considered a high sensitivity compared to average stereo speaker which makes Vestia No4 an easy to drive from Sensitivity perspective.
Read our detailed Focal Vestia No4 Review