Perverseness in "The Tell-tale Heart" & "The Black Cat"

I think the "imp of the perverse" functions differently in these two tales, but I am not quite sure. In "The Tell-tale Heart" the narrator kills the old man because of "the eye" (555), and he makes no mention of how he knows what he is doing is wrong. Also, his confession comes at a time when he is so close to being in the clear. He is driven to confess by his guilt, which cause him to confess at the wrong time. The narrator in "The Black Cat" kills the cat because of the "spirit of perverseness" (599): "It was this unfathomable longing of the soul to vex itself...to do wrong for the wrong's sake only--that urged me to continue and finally consummate the injury I had inflicted upon the unoffending brute" (599). There is no direct confession, he just comments on the structure of the house which draws attention to where he has put his wife, and then we get the sound of the cat.

Lastly, he says "But may God deliver me from the fangs of the Arch-Fiend!" (606). In "The Imp of the Perverse," the narrator says "And we might, indeed, deem this perverseness a direct instigation of the Arch-Fiend, were it not occasionally known to operate in furtherance of good" (829). So, in "The Black Cat," is this "Arch-Fiend" the cat (as I first thought), or is it the "imp" of the perverse? Or, does the cat represent the "imp" of the perverse? If the cat and the "imp" of the perverse are the same thing, then I guess that means the perverse drove the narrator to murder and gave him up to the police. I think if you treat the cat and the "imp" of the perverse as two separate things, then that changes your reading of the story.