If you listen at mid volumes (or your room is large) then a sub should be of some benefit, If you listen some of the time at low volumes then a sub will always be of great benefit. You can do the equalising thing (early amps always had a 'loudness' button!) but a good quality sub is the better way.
Will I benefit from a subwoofer with 20Hz speakers?
My source is a minidsp shd studio with Dirac going into Denafrips Gaia DDC to Denafrips T+ DAC to McIntosh 601 Monoblocks to Cabasse Pacific 3 speakers. The speaker's published frequency response is 41-20,000Hz. I presume this is achieved in an anechoic chamber. In my room however, it goes down to 20Hz, at least according to the Dirac measurements. In fact, I needed to flatten the curve and reduce by 5-20 DBs between 20-100Hz due to the room effect.
So, considering I already go down to 20Hz, is there anything else 1 or 2 subwoofers will do for my system? Would it create a more consistent low frequency field? I see many people adding up to 6 subs, so I wonder what I'm missing.
Thank you for your insight!