If I were to ever get a tablet I'd go iPad, just because they're very easy to use.
In your price range though, I'd say a blackberry Playbook would be pretty good. My brother-in-law and his family all have Playbook's and they seem to absolutely love them. Relatively inexpensive too.
I will leave my signature the same until the Toronto Maple Leafs miss the Stanley Cup playoffs. In short, I will never change my signature.