In many cases, poor or lifeless sound is as much a result of less than optimal amplification to drive a particular speaker design than anything else.
Many modern speakers with good extended low end are also fairly inefficient and/or require lots of current to drive properly. The needed amps can become big, heavy and expensive both to buy and run. Class D amplifier technology negates much of this. Or some may chose to go with speakers that are more efficient and also likely also more (lower power) tube amp friendly.