Subwoofer ?

The sub(s) should blend with the main speakers, it should simply augment the low end of what your mains cannot do. Very very few main speakers today are built full range, meaning go to 20Hz, most roll off around 30Hz to as high as 50Hz (for small bookshelf models), so you are not experiencing the full range of the music without use of subs.

Sub setup is critical to achieving a great blend, and absolutely you can hear and feel the difference with subs on, sure I have plenty of music that is very difficult to tell any difference but when the music calls for it the subs make it so much more engaging, simply because you are hearing the full range of music, and nothing can correct a badly mixed recording.

Room treatments can help, but honestly most (90%) of pictures I see of peoples music rooms trying to use room treatments is not realistic. We all have furniture, windows, door ways, halls, tables, rugs, carpet, hard wood flooring, curtains, hanging pictures, you name it.....that you would never be able to effectively diffuse and create the reflections properly to make it sound better let alone look good for your spousal unit's approval . If you don't have the gear to accurately reproduce music that has sub 30Hz frequency, no room treatment will make that come out, it starts with the gear first.

I've measured my main speakers to about 32Hz, but with my subs I have measured to around 18Hz, that's extreme though. What I get is the sustain of low notes now, a standup bass pluck can now play longer since I hear/feel the whole sustain, rather than it getting cut off at say 40Hz. And when the music has it, my room will pressurize nicely and you feel the music as well hear it......It's pretty awesome.

Are? Not really anymore. As in not a job function. Last album I did was BUSKER's Northern Fantasies.

These days my music involvement is in the form of volunteer work as the Main Stage manager at the Orangeville Blues and Jazz Festival.

I've got walls, floors and furniture.

But seriously, as a former sound engineer myself I guess you might expect that I would go to the n'th degree to tune my listening space. Only here's the thing, I don't have the budget to even come close to it. I probably spend 0.001% of my life actually sitting and listening to music. Most often it is relegated to background sound as I work. Lastly, I don't have the RTA required to make any room treatment truly useful. I came to the realization a long time ago that my personal listening space was never going to come close to my time in the studio.

I think it was reading "Perfecting Sound Forever" by Greg Milner that brought me to that conclusion. It's really just chasing the end of the universe and I have so much more to do with my life.