I have been going through the same thing lately... because I have a couple of rifle actions that needed a new barrel and I have more calibers than I really need.
Here in Alaska almost everybody has a 30-06, 300 win mag or a 338 win mag and you can buy 30-06 ammo in ANY village.. And more than likely find a few hundred rounds in any parking lot full of cars/trucks.
For the next step above a 30-06 I have been using a 358 Norma Mag and 350 Remington mag... The 35 calibers really work well up here...
So I too have been thinking about a 338-06 or a 35 Whelen.... Just because I have a rifle that needs a new barrel.... But neither did anything that my other rifles need not already do,,,,,
So I went ahead and went with a 375 Ruger chambered into a 1917 action... That puts it between my 35 caliber magnums and my 416 Taylor.
If I lived down in the lower 48, I would go with a 35 Whelen... Factory ammo and brass can be found,,,, it holds 5 rounds in the mag (unlike the magnums) and it does not have a horrible recoil. And you can make ammo from 30-06 brass.