I too loved Kate first, then Fleetwood Mac (Stevie in particular), and then Grace Slick (and Jefferson Airplane). But I'm still into Stevie and FM completely even though now Grace is there too.
And as far as Tori Amos goes, I have nothing against her. I don't actually see her as that similar to Kate. She's got her own style. Even if she's been greatly inspired by Kate, so what? I am comfortable and confident enough in Kate's complete and utter originality and unique-ness, that I have no problem with Tori doing her (somewhat similar at times) thing.