Hey Cwaigy,
I owned the Klipsch Forte II for over 15 years before I sold them about 3 months ago. They are fantastic speakers for the money, even back then. They are extremely efficient and require very little power. You can't go wrong whether you continue to use your 75 watt receiver or upgrade to a tube amp. Even a very low power tube amp will power these fine. I was using a Rogue 88 tube amp in Triode mode which translated to about 35 watts and it was more power than needed.
I owned the Klipsch Forte II for over 15 years before I sold them about 3 months ago. They are fantastic speakers for the money, even back then. They are extremely efficient and require very little power. You can't go wrong whether you continue to use your 75 watt receiver or upgrade to a tube amp. Even a very low power tube amp will power these fine. I was using a Rogue 88 tube amp in Triode mode which translated to about 35 watts and it was more power than needed.