Cheap eq pedals can be kinda noisy, your milage may vary.
An equal pedal helps in my opinion most if it's placed late in the signal, like in the amp fx loop.
If you can't do that, I don't find the eq as useful except for small changes to balance the tone of different guitars or pickups. Not for sculpting the amp sound.
If you're using distortion pedals you can experiment with eq pedals before and after, you can see that the placement of eq can make a lot of difference in how much it colors things.
That said, sounds like your 412 cabinet might be the issue.
I would say eq is not the ticket but to work on trading up to a better cab. The mx series has a different sound and eq pedals wont help that very much