I own the Active Ground Box SE and find that they make a noticeable difference, but this is true mostly because I have a full Synergistic Research loom. All of their cables have mini banana-like connectors which expose the ground. So if you have RFI or other unshielded elements nearby, those cables can pick it up through the exposed mini banana if the ground cable is not plugged in. Granted, these cables do come with their own ground plugs, so at a bare minimum, use that.
With the ground box, though, there is for sure an added sense of noise reduction that is evident. In addition to grounding my cables, I do run ground wires to each component, either through an unused RCA input or available ground tap. The result is a blacker background, more resolution, tighter imaging. This was true especially with my vinyl rig, my streamer, and preamp.
Regarding the comment about having to buy the expensive ground cables, this is untrue. If you have DIY skills, these cables are easy to build. Personally, I bought long lengths of 14awg silver-coated copper wire - mine were from DH Labs at $4,50/ft:
I then soldered these connectors on each side using WBT solder:
I’ve also soldered quality spades, rca connectors, etc onto these wires, all available from DH Labs, to assemble the different types of ground wires I needed.
Honestly given the quality I don’t think the SR grounding cables would be much better. Hope this helps.