From what I heard ( and not very much) if you got some really good floor standing speakers a sub isn't going to add much if any. I tried one of the HSU subs I don't recall the model and my old L100T's sounded much better without the sub. Not saying the L100T's are great but they smoked that sub with ease.
For music you have a valid point. As I said the other day, subs are widely abused and so often lead to less accurate reproduction.
Since the advent of subs people have come to think of bass as 20 to 80 Hz when in fact most bass is in the 100 to 500 Hz range. 500 Hz is bass period and NOT midrange. The transition to midrange is on the 500 to 1000 Hz octave. The real bass power band is 80 to 500 Hz.
This is part of what I wrote the other day.
Whether a speaker rolls off at 40 Hz or 20 Hz is almost irrelevant. What really matters is a good power and response (not just frequency response) from 40 Hz to at least 400 Hz coupled with exemplary midrange and power response to at least 4 KHz. That is what is of primary importance.
This obsession with the last octave has led to the largest downgrade in most systems since the Hi-Fi era of the fifties. The content below 40 Hz of music is small. Most organs only have 16 ft principals and a speaker rolling off at 40 Hz can reproduce it perfectly. The 32 ft stops are infrequency engaged and almost always for transient effect.
So what is the modern curse. Speakers abounding with woefully inadequate power band response from 40 to around 800 Hz, coupled to a powerful sub turned up too high in a futile attempt to cover the above deficit. Currently there is a massive abuse of subs. I would bet that goes for the majority of member systems.
Now that goes for music. However the movie industry like sonic effects and even have a channel directed to subs called the LFE channel which goes up to 120 Hz and is directed to the sub along with content directed to the sub below crossover.
Certainly you are correct that it is easy to impair fidelity with the improper use of subs, which I believe to be common.
So if you are not into movies for you a sub is not essential. Not many speakers will handle the movie situation at required levels and unless the speakers are active you can't capture the LFE channel.
There are advantages to an integrated speaker I believe and that is what I use in my main AV room, but there is a little complexity to it in the home theater environment.
Integrated speaker or not, achieving really well balanced sound is still a challenge as you have found out. A loud booming sub is the antithesis of good balanced sound and a good speaker naturally rolling off is far preferable.
