Metz karoo street seem to get great reviews from an Australian guy riding a bmw gs ... He did an invited to new zealand adventure ride and metzler tyre test . he then put the karoo str on his own bike back in Australia and said .... They had peg dragging road manors and 'flat track style' gravel road with good hook up and corner performance.I wouldn't try Avon Cobras, they are cruiser tires. If you intent on using Avon tires, I think the Trailrider are a far better choice.
(or Michelin Anakee Adventure, Pirelli Scorpion Trail 2, Dunlop Trailsmart...)
My $0.02