Amulets probably can't be destroyed, but yeah, having the Amulet removed somehow may prove a disadvantage. When Dante got his Devil Trigger energy shot out from the statue and explicitly went for his Amulet. So it holds at least some significance. Although, the Amulet may only represent a sort of key needed to first unlock the power, since the power itself comes from within the person themself.
The problem is that Vergil's Downfall was all sorta in Vergil's head, it was a personal hell he went through while he was dying. So his missing Amulet wasn't really missing, it was all a rather metaphysical experience. The whole thing was about him confronting his failures in his quest for power, and the "Hollow" people he met were just negative interpretations of his mind, probably all coming from the same source: Hollow Vergil, who existed solely to get Vergil to sever the connections to his "compassionate," human-like side. That's why Vergil's Downfall was pretty much about Vergil turning his back on and/or killing the people he knew (metaphysically, of course). Hollow Vergil made Vergil see them as obstructions in his lust for power, with himself being the last stepping stone. Beating Hollow Vergil, giving into all that anger and hatred, all that power, and reclaiming his Amulet was sort of like reclaiming the power he once had, and then some. Sorta like how you mentioned the loss of the Amulet representing the loss of power, IncaDemo.
Regarding Doppelganger, though, that's just Vergil's Devil Trigger. Doppelganger isn't a representation of his demonic side anymore than it's just a magically-projected double of himself, with all the same angelic and demonic powers. Vergil's Doppelganger was not really Hollow Vergil. As I mentioned above, the Hollow characters were just a representation made for Vergil for step over - they are legitimately just all the bad aspects Vergil could see in that particular person, which made it easier for him to leave them behind ("My brother is a dick. Kat was useless and weak."). At most, Hollow Vergil represents what Vergil could become by letting go of his personal connections - much in the same way the classic Vergil denounced his human side as weak, and threw it aside in favor of his demonic side.
Since all of Vergil's Downfall is a mostly metaphysical experience, it's entirely possible that the removal of the Amulet wouldn't have any effect, though. It's sorta hard to say :/ All of the events of Vergil's Downfall happened in such an odd place...
The problem is that Vergil's Downfall was all sorta in Vergil's head, it was a personal hell he went through while he was dying. So his missing Amulet wasn't really missing, it was all a rather metaphysical experience. The whole thing was about him confronting his failures in his quest for power, and the "Hollow" people he met were just negative interpretations of his mind, probably all coming from the same source: Hollow Vergil, who existed solely to get Vergil to sever the connections to his "compassionate," human-like side. That's why Vergil's Downfall was pretty much about Vergil turning his back on and/or killing the people he knew (metaphysically, of course). Hollow Vergil made Vergil see them as obstructions in his lust for power, with himself being the last stepping stone. Beating Hollow Vergil, giving into all that anger and hatred, all that power, and reclaiming his Amulet was sort of like reclaiming the power he once had, and then some. Sorta like how you mentioned the loss of the Amulet representing the loss of power, IncaDemo.
Regarding Doppelganger, though, that's just Vergil's Devil Trigger. Doppelganger isn't a representation of his demonic side anymore than it's just a magically-projected double of himself, with all the same angelic and demonic powers. Vergil's Doppelganger was not really Hollow Vergil. As I mentioned above, the Hollow characters were just a representation made for Vergil for step over - they are legitimately just all the bad aspects Vergil could see in that particular person, which made it easier for him to leave them behind ("My brother is a dick. Kat was useless and weak."). At most, Hollow Vergil represents what Vergil could become by letting go of his personal connections - much in the same way the classic Vergil denounced his human side as weak, and threw it aside in favor of his demonic side.
Since all of Vergil's Downfall is a mostly metaphysical experience, it's entirely possible that the removal of the Amulet wouldn't have any effect, though. It's sorta hard to say :/ All of the events of Vergil's Downfall happened in such an odd place...
Vergil lay dying on his parent's grave in the Human World
Then...
Vergil was swan diving along with other tortured souls in what appeared to be Hell
And then...
Vergil was slayin' demons and severing emotional connections with shades of people he knew in what appears to be his mind.
...in the end of Vergil's Downfall, Vergil wakes up from the grave with all that juicy new demonic power, and the demons take bended knee in servitude to him.
If anything, Vergil's Downfall could be like Dante's treks to the Lost City which helped him unlock his Devil Trigger and some other skills, because Vergil never truly left the cemetery...