Question: are 20 watt speakers loud?
Answer: The 20-watt amp is double the power of the 10-watt amp, but doubling the power only translates to an increase of 3 dB SPL. Remember, in order to sound "twice as loud," you need an increase of 10dB, so while a 20W amplifier will sound noticeably louder than a 10W amp, it will not sound twice as loud.