You may consider the Roland FP10 instead. It often comes in a bundle.
EDIT: Having played all of them, I would say go for the Yamaha P45, I definitely liked the sound more than the others. Roland felt very artificial in comparison. You can make a P45 sound good, which is something I can't really say about the Roland. The Casio can sound decent as well, but doesn't sound as natural as the Yamaha, and probably isn't good if you're learning classical piano. It is workable, but the piano preset doesn't have as much control or dynamic range from what I've seen.