Free: Contests & Raffles.
300 win mag or wsm. But why on earth would someone want only one rifle?
Tikka T 3 stainless lite in 300 mag, 300 wsm or 30-06 . Some will suggest 7mmCan pick one up for around $625. Would buy after market rings like Tally or Warne . Less than $700 spent for a very good, accurate proven rifle
Beware the man with one gun. Just guessing here...but you likely don't reload and not shoot a ton. I would stay away from the big Magnus....rum, 338,etc. The 30-06 is a proven killer to way out. The level of recoil is a bit more forgiving and will likely get you to shoot more. Nothing wrong with a big magnum...but they do beat on you a g good bite.
Of the 4 you listed, I'd do the 300WM in a Tikka.As far as the etc's, I like both my 7mmRM in the Tikka or the Ruger M77.