#1 Self-powered speakers that come with computers, thought they were terrible.
#2 Prefer class A or class AB. National's own words:
"In-band noise is higher in switching amplifiers than in linear amplifiers because of increased noise from the switching waveform."
#3 The last part of page 14 and the first part of page 15 of LM4651's data refer to optimizing the amp for low frequency.
Page 12 figure 6 shows a rather standard opamp low pass filter that is needed to make this a subwoofer amp.
In my listening room I want the highest possible quality.
While plastering & painting the house I like MP3 jukebox,
as long as there is no obvious distortion.