Okay, if you were talking about a lack of really deep bass when the alien ship lands, I would say you need a new sub, but for muddy sound that is very likely room effects messing with your bass!
I assume you have read this review by Brent Butterworth:
Brent Butterworth reviews Klipsch's $899 R-115SW subwoofer, a ported design that uses a 15-inch Cerametallic driver and an 800-watt Class D amplifier.
hometheaterreview.com
Here is a relevant quote from that article:
It is an unfortunate truth that reviews declaring this or that gear as amazing are "dime a dozen", but IME, Brent is of a different class. For starters, he takes measurements when he reviews a sub, but more importantly, he is a pretty good bass player in a Jazz Quartet, so is intimately familiar with what bass should sound like.
Here is a piece he wrote and performed. My understanding is they mixed this together since the virus prevents them playing in the same room.
So here is what I would suggest for you:
1) Switch your AVR to direct or pure direct. Find a piece of music that you experience as being muddy and listen to it to refresh you memory of how bad it is and the specific places where the muddiness is obvious. You may even want to write down the time of the offenses.
2) Move the sub out into the middle of the room; say, at least 4 feet from the nearest wall. For the purpose of this test (this is a "quick and dirty" test) I would not worry about re-running setup.
3) Keep the AVR in direct mode and listen to those same places and see if you have the same "muddy" experience as you had before.
4) If you did not hear a big difference, move the sub 2' in any direction (except towards the walls) and listen again.
I suspect you will experience a different behavior. There may still be problems, but they won't be the same problems. This is a poor approach, as it is simply "trial and error", but I suspect it will be enough to demonstrate that your room is a major reason for your issues. Also, whatever effort you spend improving your sound with the Klipsch sub is almost certain to have a similar pay-off with any new sub you get. Buying dual subs will certainly improve, but it is important to get an understanding of these effects so you can better address them.
If moving your sub around is difficult (especially if on carpet), these are handy and make it easy to slide:
Read reviews and buy Scotch Reusable Sliders at Target. Choose from contactless Same Day Delivery, Drive Up and more.
www.target.com
You might want to do a little research to understand what is happening (but we are always willing to help you tune things).
Here is a nice article that will help you understand what happens with bass in a room and a video on one of the ways to optimize location of your sub.
Even if you live in a studio apartment, you have at least two listening rooms. Well, in a sense. Every listening room is, in essence, two listening rooms when you look at it from the perspective of sound.To midrange and treble frequencies, your listening room is like a billiards table. Like...
www.soundandvision.com
And here is a nice video on the "sub crawl":
HTH!