7 mag would be my choice from your on hand options. Single load of a hard-ish (probably monometal) 160 weight class bullet at about 3000-3100fps.
From your choices and buying new, id go with the 7-08 and 140-150 monometals.
2900 with a 140 is plenty enough oomph for most things.
I do think the 6.5s hit a sweet spot for this type of use. The creed to PRC performance range being the most practical.
If i wanted to shoot a less common round ds go with the 6.5-284, or x55 in a tikka t3x or similar.
Either of those should be able to drive a 140 grain glass projectile at about 2900-3,000 feet per second. That will actually duplicate the trajectory and, in my experience, penetration of a similar 160 grain class 7 mm bullet at the same speed.... Kinda like a 7 mm Remington Magnum light.
Again, if you shoot monos, you should have less substantial damage done to smaller targets.
As others have said tho, you can have your cake and eat it too with a swap barrel. Im assembling another on a savage 111 action thats ostensibly going to be my dads long, long range rifle, as well as his hunting rifle.
In your case is probably do a 6mm CM and a 300wm or something similar....Encore makes it alot easier, and probably what i should have done
....cept im not an encore fan.