Virtually free system upgrade?

I had a recent experience that I want to share with my fellow (and lady :-) ) Audiogoners. I added a Hsu VTF-3 subwoofer to my system a couple of months ago. It came with a test tone CD and correction factors for using a Rat Shack sound level meter with it to check the freq. response of the bass. On nearly every bass tone, I heard stuff rattling or buzzing, and I realized that I could not get accurate measurements with the extraneous noises. By banging my fist on the walls where the noises originated, I found and quieted a picture frame and window screens that were rattling, found the sheetrock on one wall rattled at 20 Hertz (nothing I can do about it unless I want to shoot screws, spackle and paint the whole room, which I don't), but I found the major problem to be the baseboard heaters along the wall behind the speakers/sub. I spent over an hour working on the b'boards and got 'em MUCH quieter. I wasn't in the mood to take measurements at that point, so I put my CD changer on random play for background music, but before I could leave the room I realized the sound was much better, and not just the bass. A certain overhangy quality in the bass (a sound I used to think was inherent to Hsu's subs) was completely gone (I detest the constipated bass most reviewers seem to crave, but sloppy bass sucks, too!) and the bass sounded much cleaner, but the real surprise was that the attack and clarity of EVERYTHING (including xylophones and cymbals) improved radically, too.
I'm still trying to get the measure of the extent of the improvements a week later. I've come to realize that the baseboards were causing problems long before I got the sub (I confirmed this by turning off the sub and noting the improvements over what the system had sounded like before getting the sub), and in most, if not all, of my previous systems. Try it for yourself. I used toothpicks, piece of rubber and pliers to quiet the baseboards. I wedged the toothpicks between the vane that opens or closes to control the heat and the hinges for it, and used the rubber and pliers on the baseboard covers and their attachment points. I'll probably redo it with self-adhesive foam (it's a pain in the butt when the rubber falls out).

If anybody tries this, post the results here.