It's in the least hinted when Sabriel became Powerbonded that, though her Amulet was destroyed, she herself was not (her original, non-Powerbonded form appeared to Sophie prior to becoming Powerbonded).

The main example, though, was shown in S2E50 when Legion was defeated. Though the Titans' Amulets were destroyed by their being absorbed by Legion, the destruction of Legion's Amulet showed a release of a plethora of previously absorbed Titans returning to Huntik.

Also, though there is not nearly as much data on Huntik's ancient past, it would make the most sense taking into account the initial creation of the Amulets by Casterwill so that he could summon the Titans to Earth. This would logically mean that, at one time, the Titans existed in Huntik (the Spirit World) without the need for Amulets. They just were unable to be summoned to or influence the physical world.

All this to say, the destruction of the Titan's Amulet just severs their ability to remain invoked in the physical plane. There currently isn't anything to indicate any circumstance that actually destroys the Titan itself - on a related note, I recall that earlier on, many thought that Titans had been destroyed when they had simply been sent back to their Amulets.