Dude!! You are hitting it on all angles right now! Im seeing you posting everywhere! Hope you are absorbing all that you are learning right now
MY first suggestion, and the cheapest way to try some things is first speaker placement. If right now they are shoved into corners, pull em out, put them in a few different spots.
next try toeing the speakers in towards the listening position, or sometimes, even toeing out works depending on the room.
next get a heavy blanket or two and drape them behind or to the outside of the speakers and see if taming the first order reflections makes a good difference. if you have several blankets to demo out, use em all and see what you get! This is a no cost, easy way to TEMPORARILY treat parts of your room. pick a few songs or movie scenes that you know up and down, and see from the main listening position if it makes a difference. If you decide some sound absorbtion is needed start looking at acoustimac.com for some pretty cheap absorbtion panels, you may only need a few to make enough difference for you.