1) The Yamaha subs most likely can't keep up witt he mains

2) Those are incredibly efficient main speakers. How loud do you listen? Yeah, you can crank it but the sub is gonna run out of steam long before the speakers.

3) While those speakers may be "loud", they really don't go as "low" as you would think. If you try to "force" them to do subsionic by turning it up, you ARE gonna run out of power. ...and don't expect the yammie sub to perform miracles.

4) Sometimes, that "congested" sound you are complaining of comes from inside the ear itself.

5) You CAN play too loudly for a room and that can screw things up. All that SPL has to go somewhere, and it's reflected all around and can cancel itself out.

6) You simply may not like the sound of the speakers.

7) Given the above possibilities, your expectations may be unrealistic.

Here's a little primer on power and how you hear it.

1) A gain 3 decibles is barely noticable.

2) To realize a 3 decible increase in preceived loudness during peaks you need 2x the power. IOW, if you're pushing 60 watts, you need 120 to meet that goal.

3) A gain of 10 decibles results in an apparant doubling of perceived loudness.

4) To realize a 10 decible increase in preceived loudness during peaks, you need 10x the power. IOW, if you're pushing 60 watts, you need 600 to meet that goal.

Where do you want to go from here?