I have lusted for Infinity RS 2.5s ever since I heard a really well set up pair at audio fair in Milan, Italy , way back in 1979. The "cookoo clock" appearence of those EMIM midrange drivers while playing hotter parts of Telarc's recording of Mussorgsky's Night on Bald Mountain is a lasting memory. Please let us know how HA-S500s ( after a leeeeenghty burn-in they neeed so badly ...) stack up to RS 2.5s - it has been decades since I heard RS2.5s now, but I think they should sound pretty similar - if the RS2.5s have enough juice feeding them and enough place to develop in all their majesty. RS2.5s are one of the top three speakers ever produced by Infinity - out of the contenders for the throne within that brand in period it did build serious speakers, the only one I never had a chance to audition is the Servo Statik 1.
You should find HA-S500 a real treat - believe me, you will never regret spending those $ 79.