Efficiency is a relative rating. My speakers are officially rated at 90 dB. However, the manufacturer recommends a minimum of 100 watts, and "200 watts for full musical enjoyment". I've tried many different amps over the years and ended up with 400 WPC amps (at 8 ohms, my speakers are 4 ohms).
So, how can this be? I don't know how the 90 dB rating was identified (I suspect from the driver manufacturer, but who knows?) but they are less efficient than some speakers with lower ratings. It could be that more power is needed because of the impedance curve across the frequency band - they dip below 3 ohms at two points. Or it could be the complexity of the 1st order crossover. A friend who knows electronics looked at the crossover board and jested that all it needed was an input transformer and it could be it's own amplifier.
On paper you should get at least 105 dB from a 100 WPC amp driving a 86 dB speaker. Even allowing for headroom, that would be adequate for most of us in an average room. But all this relates to level before clipping, not "final sound quality". I don't think your question can be answered by anything other than a personal evaluation.
