All your options have merit but get what you really want. I have several 243s and won't change them but after years of wanting one I am finally doing a 6mmAI. Will it greatly out perform the others, probably not. But since each rifle has it's own dedicated ammo it will be easy to keep the 6AI separate. And I can play with the 115 grainers if I choose to.
For me a Browning low wall .243 fits the light weight niche and is a joy to carry. If buying new I would look long and hard at the Barret and forego the bargain rifles that may loose their appeal fairly quick. If miraculously I shot out the 243s all at once then the 6CM might get the nod.
Ditto on the Low Wall. My Hornet is probably my favorite rifle. A matching .243 would be sweet. I see them from time to time on GB, but not when I had the bucks, yet anyway. I did have the money when a NIB Traditional Hunter .44 appeared, and now it ain't NIB anymore!
