I think if it's in north america and you can't get it done with a .270, then you're not going to get it done with a .300WM. Yes, there's more energy there, and more bullet weight, but is it disproportionately more powerful? Eh, not so much. A good bullet, well placed, from a .270win will kill anything in the US.

If you want something "bigger," and are convinced that the 30cal's really are significantly bigger and more powerful, then I'd be spacing it out far enough to make it worth it. Get into a .300WM or WSM.

Another advantage of NOT getting a .30-06 (can't believe I'm advising someone away from an '06!!!) is that mixing up a .300WM and a .270win cartridge is pretty difficult. Mixing up a .30-06 and it's little brother .270win is pretty easy.

If you really want to step up to a harder hitter than a 30cal. Look into a 338-375" diameter. I'd love to get into a .338-06 or .35 Whelen, even though she's none too quick. A .338WM might be a little more in line with what you're looking for. .375 H&H will knock the tar out of anything u touch with it (yourself included-get a pad, get a brake).

So moral of the story, either get a .300wm or a .338wm.