Looking at the sleaker spec sheet, the manufacturer specs them at 90 db and yet recommends between 30 - 200 watts for them. Do you think you can find a tube amp to fall into the higher end of that bracket?
Remember, these are two small drivers and, due to the 2:3 law of speaker design*, generally require more power to deliver satisfying bass.
*2:3 law: High efficiency, bass extention, small enclosure: Pick two, any two. ...but you can't have all three.