I believe your post said ultimate rifle?? Not cartridge??
I personally have a 340 Weatherby mangnum. And it is a real elk killer. So it would be one of the ultimate cartridges. Problem with the 340 is the weight of the rifle.
If I had it to do all over again I would buy a Kimber Montana in 338 Federal. Or the 325 WSM.
I think that would be the ultimate affordable rifle and cartridge selection for an elk rig. Tom.