Aside from greater potential to blow up speakers accidentally, excess power in-and-of-itself is not a problem. But, in the real world, how one gets there—running many output devices in parallel— could reduce sound quality. Many years ago, I heard a demonstration of two Rowland amps that were very similar in build, one rated at 50 watts, the other something like 200 watts, running power hungry Magneplanar speakers; I preferred the 50 watt amp, particularly at lower volume levels where the big boys sounded lifeless. One manufacturer of high end gear touted how his amp used only two output transistors per channel, that is, until market demand compelled him to make an ultra high-powered amp.
I run high efficiency speakers, and with my speakers, the very best sound I’ve heard comes from low-powered tube amps. One of my amps is an Audio Note Kageki (parallel SET 2a3 rated at 6.5 watts/channel), the other (my favorite) is a custom-built pushpull amp running 349 output tubes (5.5 watts/channel). I also liked, in my setup, a First Watt J-2 solid state amp that is low powered. Perhaps I do compromise sound at higher volume levels, but I rarely play my system at high volume levels, and even when I do do, the average output would still be below one watt, and I choose not to compromise that watt with amplifiers that don’t sound as good.
