It's simple, if you are serious about achieving great sound there are two requirements: room treatment and a DBA system. Read articles from Welti, Floyd and Geddes
This will lift your system above the pedestrian, that is any system not employing subs.
There is a scientific goal with treatment where the quest is to get the sound to decay a certain amount in a certain time and only broad-band absorption including bass traps will provide this. Those mentioning books as diffusers and drapes and other silly things have little effect.
EQ of course can not know how long the sound takes to decay and even if it did what can it possibly do? All it can do is boost or attenuate and there is a limit how much it can boost before your amp runs out of steam. EQ is not necessary in a good room.
I helped a friend where we installed 3 small 8" subs, the lowest we got from some scavenged drivers is about down to 45Hz. which does not really count as a sub but overpowering bass was not the reason for doing this. These 3 small sealed boxes provided a large number of peaks and partial nulls that were very much less than before. So what we ended up with, beyond the 32Hz of his main speakers was a smooth response from about 50HZ upwards. Some full nulls had been filled in that had previously cancelled any music info. In other words music previously completely absent was now heard and the overall effect was truly amazing with a sweet spot the width of the speakers. Everything improved. Consider also that no component upgrade can do what I have just outlined.
As I said, if you're serious!
No subs are the domain of the bootless and unhorsed 😁
