Subwoofers - crazy upgrade!

@cdtd 

Elevating your subwoofer might decrease your volume/gain because you are moving it away from a boundary which serves to reinforce the output. But as always, try it and see if you like it.

SVS sells isolation feet that bolt right on to their subs, I have them on all my SVS subs and on a pair of Klipsch LaScala speakers. Well worth the money in my view. As others have pointed out... if one sub suits your fancy try two. When I added subs 20 years ago my love of music harkened back to my teens and twenties. It was like starting all over again. The CD by Herbie Hancock / Dis Is Da Drum took on a whole different meaning to me. As has much music. Once again, the adage "it's never too late" rings true.

I’m still using my circa 1999 Velodyne SPL1000 10” sub. Never tried another sub or a 2nd unit. Probably my loss.

If you stack subs, doesn’t that introduce vibration

into each sub, causing distortions?

This is a little excessive but it gives you something to dream about when you’re talking about stacking subs. https://share.google/PGq3mBI8pqe3sAbXq. 
 Now that you have discovered bass. Don’t overlook the need for room treatments, it too can be just as transformative. Good luck 🍀 in your stacking journey!