I am a Siren.
PS: Get a QSS as Kha vs. Veigar and you will 100-0 him, but by the time you can afford it you'll likely be out of the laning phase. IDK if I'd build a Hexdrinker against him because he'll probably burst right through it if he manages to pin you down. QSS can build into Mercurial which carries the magic resist, active effect, and adds the AD that Kha needs. I don't find it very difficult to play as Kat against a Veigar, either. You can pretty safely E out of his cage if they're bad.