Welcome to the forum RahmanAron.
Your post doesn't contain a question specific to MusicBee.
So it is better suited for the 'Beyond MusicBee board, and it will probably be moved there by a mod.
For advice on speakers and headphones, there are fora on the internet that are much better suited to answer your questions, or already have the answers if you search them.
But to address your equaliser question:
Hard-line audiophiles will say you should never use an equaliser because it will change the sound of how it was intended by the artist/engineer, it will introduce different sorts of distortion, it would only be needed to compensate for inferior equipment, and that it will work like a drug. (you will get used to it's non-realistic enhancements of the sound)
There probably is some truth in all of that.
A music/audio lover with both his feet on the ground would 'allow' and use it for listening at low volume levels, to compensate for recordings that just don't sound good on your audio system, or for compensating some problems that your listening room may pose with regards to resonance, dampening or enhancing frequencies.
But as a start, on your quest for headphones and speakers, begin with setting up MusicBee for bit perfect playback without using any effects or equalisation.
Get accustomed and appreciate a clean sound that may sound a bit thin and analytic at first.
You can always add some warmth or dynamics later when so desired.
But you can never get equipment that has some warmth or character by design to sound clean and transparent.
(edit just before posting, I see sveakul beat me to it, but I think our replies strengthen and confirm our ideas about the matter)