Normally, large overstuffed couches act as bass-traps in rooms. From what I've looked at, you get the most bang-for-your-buck by treating the corners of the room with traps, floor to ceiling. As a cheap check, you can steal some couch cushions and stack them up, see if you can measure any difference by placing them in different areas and corners relative to the room.
To absorb a significant amount of low-bass energy, your foam/treatment needs to be quite thick. 2" egg crate isn't going to tame any bass issues. Generally if you can treat 1/4 wavelength of any trouble frequencies you can tame them very effectively. Raggedness between 150-400 is where treatment is normally the most dramatic.
If I were to treat my room, I'd do 45degree bass traps in the front corners, and also treat between the speakers on the front wall as well first, and then fill in from there if that didn't take care of the bulk of the issue.