I second the vote for a Weatherby Vanguard Sub-MOA. It gaurentees it's accuracy andis made in the USA. Plus, it has some other really cool features, such as the ported bolt and shrounded bolt sleeve, so if a cartridge ever ruptures, it goes out the side, not into your face. If they made them forlefties (and I had extra money to spend), I'd be heading out the door to get one.

As far as the cartridges you listed, I'd go for either the 308 or 30-06. You'll have more choices than with the 270 WSM.

Good luck