I have RS-52s and they sound great. I've upgraded all my other speakers, but have kept the RS-52s.
If money is a issue, buy used. Used speakers a few years old will sound as good a new speakers. Also high end audio stores may carry used speakers with a warranty.
RS-52s are a match for your RF-82s, but RS-42s should sound fine.
I do agree with the earlier post that you should upgrade the RC-52. Your center should be a RC-62. The RC-64 is amazing, but its not a perfect match for the RF-82s. I would only buy a RC-64 if I was planning a future upgrade to RF-63/83.
I personally would spend my money first on the center then address the rears. While watching TV, 70% of the sound comes from the center speaker.