For a lighter caliber, have you given any though to 25-06? I like it a bit better than 243, and there still is plenty of available ammo for it. It offers very good ballistics up to, and a little past 300 yards with store bought ammo. If you begin to load for 25-06, give me a shout, I have some good loads for this caliber.
If you don't handload, I would think twice about 243WSSM or 257 Roberts, as I don't see those much on the shelves around here.
Between Weatherby, Tikka or Savage, I would have to go with a Savage. Ain't the prettiest things around, but have had great luck with them, and they have all been very accurate out of the box.