recomending power to speakers

I currently have a pair of thiel 1.5. I am also currently using a audio research d-60 amplifier for them rated at 60 watts / channel @ 8 ohms.

I see that in my speaker manuals the speakers are rated at 4 ohms (3 ohms min) Would this make my amplifier closer to 100 watts at 4 ohms?

Also, I do have the upgrade bug and realize my amplifier is the weakest link. What do you guys recommend as far as power linked to Thiel 1.5's I have tried them with tube amplifiers with terrible results.

Thank you,