I frequently have to change the bass channel level depending on the recording. Some recordings are too hot and some are not hot enough.
I don't know if it's been mentioned but here are a couple of other things you should try. First, try increasing the level of the 60s and turning down the Polk. You may have the Polk set too hot thereby giving you flabby, floppy bass because the higher harmonics don't have enough volume.
I was going to say also try changing the distance of the sub in your receiver but I remembered that you don't have that capability. If it has a variable phase control try varying that. It could be that the timing between the sub and your 60s is off. If the timing isn't right, the fundamental and the overtones will be out of phase and it won't sound tight like it should.
If all else fails, you need to try that sub at someone else's place or bring another sub to your place to see if there's a difference.
