I would have said the 30-06, but since you mentioned brown bears, I'd definitely go with a 300 Mag. Tell you the truth, I'd rather have a 338 for that purpose, but the 300 with the right bullet will do the job. Since you're buying a new rifle, you might as well get it in the new 300 WSM, if that is an option with the Tikka. For a scope, go with a Leupold VX 2 in a 3-9x40mm.