Hooking up a separate EQ means that your audio signal is now travelling through each one of those little sliders. Unless you are spending large amounts of money on a pro eq, I don't see how this can improve the sound, it will add noise.
As BrenR states, unless you know what you are doing, and you should be a professionaly trainined audio engineer to answer yes to this question, an external EQ is a toy you will never stop playing with. I know, I had one in the 80's. It is also really easy to damage speakers with these things. I know, I did that too in the 80's.
I try to keep the audio signal as pure as I can, no EQ for me, thanks.
paul
