In the end its all about bullet placement with a good bullet. Im not a big bore fan. Right now Im considering having a light 7mm-08 built up with a McMillan "Edge" stock and a # 21/2 Pac Nor barrel ................
You might also want to consider the .284 Win, almost identical to the 7mm-08, except for the 35 degree shoulder - originally designed to obtain greater ballistics than previously possible with a short action cartridge while using a standard bolt face.
Add the 6.5x55 (or AI) to Submoa's list.
Another consideration is the .270 Win (or AI) and .270 WSM, esp with Matrix's 165/175 VLDs and upcoming Berger's 170 VLDs.
I too am a fan of the .300 Win Mag but we all know it's all about shot placement and knowing the the rifle's limitations and shooter's capabilities.
Good luck! Happy safe shooting/hunting.