All the calibers listed here are great. No matter what you end up with you need to get out and shoot it a lot. Hitting a paper plate at 100 yds is not acceptable, shooting with holes touching is. I have seen too many people shooting 6" groups @ 100 yds and think they are good to go. Whatever you buy figure out what ammo you are going to use, buy plenty of it, and spend time on the range.
Personally I like the rem 700 platform in .308, but 300 win.mag is a top performer for sure.