I am riding my Tenere 660 on Siracs tires at the moment. Altogether Siracs are good choise but do not expect to much of handling on dirt sectiones and in loose gravel. Count that tyres need warming-up time and that its become a bit of slipery after aprox. 10.000 km. Durability if very good, my rear is now 12.000 km and on paved roads it will last surely 16-20.000 km. You can ride very safetly on hard offroad surface ang grip is correct, but always bear in mind that Siracs are infact street tyres, not basicaly offroad. For trip as yours, better bet on more enduro profile as T63, it will last much less, but offroading will bring you more fun and T63 are very good on asphalt roads. Probably you count on durability on trip such as yours, so looking that eyes Siracs seems as reasonable choise.
AnteK, XTZ 660