I went through this search a year ago and came to the conclusion that you will not get true weighted keys for $500. I already had a Casio WK7500 and because I had done all my playing on an acoustic piano I literally couldn't play the Casio without making all kinds of mistakes.
I was nearly taken in by such descriptions as 'semi-weighted' keys. They really are not much better than "synth keys"
I eventually bought a Yamaha CP33 for $1000 and the feel and piano sounds are great - I can play again!

Tony