A week ago I sold my~ 10 yo SVS powered subs. While they added weight, they weren't high quality 2 channel subs. I didn't realize how much they set my sound back until they were gone, and I moved he speakers back ~ 2ft, now ~50" from the front wall.
Tonite, I finally got around to taking my Emerald Physics 3.4s off the Harbor Freight dollys which they've been on since I got them over a year ago. Each base is resting on 4 full spring Nobsounds. Quite an improvement in weight and bass fullness