Speaking of speakers... The biggest difference in "sound character" between different speakers is frequency response, and you can adjust that (to an extent) with equalization.Yes, the frequency responses aka polar response, the FRs in every direction, are the most correlated to SQ. We hear a combination of direct (on axis) and indirect (off axis/reflections).
EQ is a sound power adjustment. Whenever you cut or boost, both the on and off axis is affected. Beware, especially if based off single point pressure measurement.
There are limits to what EQ can do, especially at low frequencies where the laws of physics come into play. i.e. When you boost the bass, you can end-up overdriving the speaker or amplifier. And, there are room acoustics issues that can't be corrected with EQ.The key is not trying to fill any nulls by boosting. Cutting peaks, judiciously, is fine. Boosting the overall bass a bit for lower volume listening is fine. As a matter of fact, the Yamaha I mentioned earlier has a clever variable loudness control for just that. Also, boosting the low end of a tower to extend it a bit at low to medium volume is fine. You could counter by cutting say <20hz to keep excursion in check, especially with vented systems which most home speakers are.