RE: 300 WSM
Interesting discussion. I went with the 270WSM for a number of reasons, but can't make a statement that I "needed" the magnum cartridge. I came across a statistic a while back, it stated that the average shot taken was something like 325 yards, average kill was around 175 yards. If you look at those as the average, there's a great many hunters who don't "need" a magnum of an type or caliber.
I'm not saying that you shouldn't get one. Heck, I've made the jump. But find the rifle that "feels right" for you, with the round that'll hit at the distances you'll be shooting. If you want a bigger caliber or a magnum cuz it gives you room to grow, go for it. Ammo availability and price is a valid consideration, but as someone on this board put it, the box of ammo may be one of the least expensive parts of the whole trip.
Whatever you choose, I wish you good shooting.