IMO.... I value speaker Sensitivity over Impedance.....especially if they're not being driven below 50 hz.
Lower than 80 hz...you need a woofer/subwoofer that can cleanly re-produce the bottom octaves.....This is were Big amps and Massive Magnet brigade come into play.
At the end of the day....Your "taste" in music and "tolerance" in loudness... matters most.
Do you prefer Treble......Mid-range.......or Bass?