Perhaps the first of the Ground Enhancers was the Acoustic Revive RGC-24. A wire from one of you components goes to a metal cyninder that contains Tourmaline and "other" minerals.Especially when attached to an unused RCA input of a preamp, there is a significant effect. High frequencies are diminished with the effect being a blacker background and better imaging.
The Synergistic Research Grounding Block is somewhat different in that the Grounding Block also plugs into the ground of a wall socket. Unlike the Acoustic Revive product multiple components plug into the Grounding Block. The effect on sound seems to envolve more frequencies than the Acoustic Revive unit.
I have tried both products in my horn speaker system and in my dedicated headphone system. Both systems due affect a significant change to the system's sound.
I think both are worthy of trying.
I have not tried the Entrigg System. It is very much more expensive but has a myriad of options. There is a thread about this product at the Whats the best Audio Forum that runs for 16 + pages.