FYI, the smaller the room, the squarer the room, the worse bass you will have (bug peaks and nulls).
When the sub is playing, move around the room to see if you hear big variations. That will give you more hints than anything else.
And again, please try the sub at various locations in your room. The more room-related changes you make, the more you may know if a sub change will help you or not.
If you have bass-cancellations, you can have 4000Ws, it will get cancelled just the same.

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