But the Rings don't make them more powerful in themselves - they become enslaved to Sauron & its basically his power which they manifest, not their own. Its more a case, I think, of Sauron being more powerful than the Elves - yet even he was no undefeatable. He was beaten by Elendil & Gil-galad, even when he had possession of the Ring.
The power thing is a difficult issue, as this 'power' is more a negative thing than a positive one. It is a 'power' to negate, consume & destroy, not to create & build. The power of the High Elves could drive it back - hence Glorfindel could drive back the Nine simply by approaching them. The Light of Aman was in his face: he had seen the Two Trees before they were destroyed. The Darkness could not stand against that so the Nazgul were driven back.
I think that what we're dealing with is not a contest of strength - whether the Elves are stronger that the Nazgul in the sense of one human being more powerful than another - but of different 'forces' creation vs destruction, life versus not death but 'unlife', Light versus 'unkight'. Or 'presence', being, versus 'absence', unbeing
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