"Where should the vocal image be?
1. On the same plane as the speakers.
2. About mid way between the listener and the speakers plane.
3. Right up to the listener."
Whatever the musical material dictates. To me the in audiophilia often touted behind-the-plane-of-the-speakers presentation lacks overall immediacy, hereby loosing the ability of contrasting the source material properly. The converse scenario, albeit less frequent to my ears, is hardly desirable either; one is too stale and polite, the other too insisting and fatiguing even. Contrary to what many may expect though immediacy doesn't necessarily equate into "up front," but ideally alludes to a sense of presence - quite vital for music to come alive, as I see it.
Height of presentation hasn't been mentioned, it seems, but here I'm not thinking of raising the acoustic center as much as the acoustic field from which it emanates. A taller speaker plane appears less restricted and thus also supports contrast of presentation.