When I said you will perceive little differences depending on where you put it (B4 router, after router, switch, or device) I meant little differences between each of those. The overall effect of putting it in the spot that worked best for me I don't feel was just a subtle difference..the kind where you think maybe something has changed.
I got the sense it cleaned the sound up. Tightened the soundstage up a tad but in a good way. Better focus. Initially I felt it softened the bass dynamics a bit but I feel it improved on the 3rd day. I've read it needs a lengthy burn in but it's a passive device and I'm not too sure if that's true. Obviously YMMV depending on your set up but I feel it's a cheap enough try along with a trial period most places you can purchase it so I'd recommend trying this budget device. I have no affiliation with this product.