Arda Healed vs. Arda Unmarred (or Good vs. Evil)

[Curufin]

This is a concept that has fascinated me since I first read 'The Lost Tales' years and years ago.

In The Music of the Ainur in The Lost Tales (1), this quote has always fascinated me:

Thou Melko shalt see that no theme can be played save it come in the end of Iluvatar's self, nor can any alter the music in Iluvatar's despite. He that attempts this finds himself in the end but aiding me in devising a thing of still greater grandeur and more complex wonder: -- for lo! through Melko have terror as fire, and sorrow like dark waters, wrath like thunder, and evil as far from my light as the depths of the uttermost of the dark places, come into the design that I laid before you. Through him has pain and misery been made in the clash of overwhelming musics; and with confusion of sound have cruelty, and ravening, and darkness, loathly mire and all putrescence of thought or thing, foul mists and violent flame, cold without mercy, been born, and death without hope. Yet is this through him and not by him; and he shall see, and ye all likewise, and even shall those beings, who must now dwell among his evil and endure through Melko misery and sorrow, terror and wickedness, declare in the end that it redoundeth only to my great glory, and doth but make the theme more worth the hearing, Life more worth the living, and the World so much the more wonderful and marvellous, that of all the deeds of Iluvatar it shall be called his mightiest and his loveliest.

This seems to me to be saying that life will be better because of the marring. This is supported in later texts:

Further quote, from HoME X, Annals of Aman:

But at that last word of Fëanor: that at least the Noldor should do deeds to live in song for ever: he raised his head, as one that hears a voice afar off, and he said: ‘So shall it be! Dear-bought those songs shall be accounted, and yet shall be well-bought. For the price could be no other. Thus, even as Eru spoke to us, shall beauty not before conceived be brought into Ëa, and evil yet be good to have been.’

And from Athrabeth Finrod ah Andreth:

'This, then, I propound, was the errand of Men, not the followers, but the heirs and fulfillers of all: to heal the Marring of Arda, already foreshadowed before their devising; and to do more, as agents of the magnificence of Eru: to enlarge the Music and surpass the Vision of the World! For that Arda Healed shall not be Arda Unmarred, but a third thing and greater, and yet the same.'

And from the footnote to that part of the Athrabeth:

'For Arda Unmarred hath two aspects or sense. The first is the Unmarred that they [the Eldar] discern in the Marred. . .: this is the ground upon which Hope is built. The second is the Unmarred that shall be: that is, to speak according to Time in which they have their being, the Arda Healed, which shall be greater and more fair than the first, because of the Marring: this is the Hope that sustaineth.'

So, this seems to me to be saying that the beauty of Arda Healed (a greater beauty than Arda Unmarred would have been) is because of the Marring of Arda. An idea that having seen evil and misery, good and joy are that much more dear, perhaps?

So, my question is, re: good and evil - if Evil is good to have been, and creates greater beauty than good could have on its own (as these quotes seem to be saying) is Evil really, well...evil? Despite what Mandos replies in to Manwë's comments on my second quote ['And yet still be evil'], it seems to me that looking at it this way, Evil is not the opposite of good, but the complement of it.

Just ideas. I'd love to have comments.