Hi Spud.. good to see another 6 MPS in WA... we greatly out number the 3's. Diff whine at that speed in fairly common. I have it. If you lift the handbrake slightly it will go away because the rear diff is disengaged so it's nothing to do with the tyres. I dont think the whine is a major problem, more annoying then anything else.
I can't recall any track days (though i'd be up for that) but we do have the occasional cruise. I think one is currently planned for the 11/06/11