I would say, get the Tyros 5..
A much better machine in my opinion, surely the Casio has great stuff inside, but it's still a Casio, and i know this is a Casio forum, but let's all agree that casio's unfortunately have very little value when it comes to the 2ndhand market, unless we talk about the MT-68, SK-1, VL-tone, stuff like that..
But why not see if you can also keep the Casio by it's side? You can combine best of both worlds!