If you want to determine whether the Jensen will help or not, try unplugging the cable TV coax from the cable box and see if the hum disappears. If it does, the Jensen's the best bet. If the hum is unrelated to the cable TV service, the Jensen will probably not help at all.

If the hum is the same at any volume position when the source device is not playing anything, then it's unrelated to the volume control. That definitely makes checking for cabling issues a worthwhile exercise - make sure connections are tight and that power cables aren't crowded alongside speaker or interconnect cables.

How close to the tweeter do you have to be to hear the hum when nothing is playing? If we're talking a foot or more, I'd certainly keep searching, but if we're talking about an inch or two I might not get too caught up in the "hum hunt."