Better magnets will be more powerful, don't buy into magnet weight numbers. Many drivers use smaller magnets that are better (such as ceramic, neodymium(tweeters), etc.) and do very well. Motor strength is what matters, and that depends on both the magnet and it's relation to the voice coil. If the speaker has a tight gap, it will have more motor strength than a speaker with a looser gap. Too much magnet will overdamp a driver and negatively affect SQ. BL is the thiele-small parameter that defines motor strength, the higher it is, the more powerful the motor is.