Your "good" CD's are more phase coherent, which in your case, is working against you -- because you have dipole speakers which are (I'm guessing) fairly close to the side walls? but pretty far out (> 3ft) from the rear walls? you may be getting cancellation around the outside edges of the speakers -- more pronounced with well-engineered recordings.
If I guessed right, then what you need is more absorption (drapes, blankets, absorbent panels) going about 6ft each way from the two back corners (behind the speakers) of the room.
If I guessed right, then what you need is more absorption (drapes, blankets, absorbent panels) going about 6ft each way from the two back corners (behind the speakers) of the room.