Re: How Far is too Far
I think you're right on the money. I have a heavy barrel 243 that shoots sub 3" groups at 500 meters (547 yards) but I'd never consider shooting a deer at that distance, because I don't think it'll deliver enough energy to effectively kill a deer at that distance. Also, unless you practice at long range, even with heavier or "magnum" calibers, you aren't very ethical slinging lead at animals that are too far for you to be shooting at.
As for optics, the more the better in my book. I'd rather have a 14x or more scope than a 9x scope out west. You can see a LONG ways out there, and more power is better in my book. You might not need 14x or more, but it may help in judging animals, seeing horns, etc. You can't hit what you can't see.