Been looking at the OS map, and I'm pretty sure that the Barr is not visible from Achnabreck. Dunnadd may be visible to the west of North. If it is then it'll be in an unusual way, just peeping around or over other hills, or possibly cradled between them. You ask if its got "a *very* significant and *very* sacred hill on the skyline" - if Dunadd is on its skyline then this would more than fit the bill, as I'm sure you know!
Of course this is the place where the Irish Kelts are thought to have first come to Scotland, so you'd expect some parallels with Irish sites...
Exciting Stuff!