I've been going down the same road for bit now. At the end of the day, I'm looking for a 500-600 yard elk capable rifle, with a 22" barrel, and set up around 9lbs, so I don't need another 3K+ custom rifle to do it. I'm either going to buy a mesa, or tikka and cut the barrel down to 22" and thread it. I have 7rm brass and dies, so that's what I'm doing. I do think some of the other cartridges may best it by a little bit, but not enough to matter to me for the hassle. A 162 @ 2850 is really all I need, I think it will do a bit better than that. 7 saum would be my first choice for sure, but would end up costing me a lot more money for a rifle that won't best what I'm doing by anything other than being a short action....which would be nice but not worth it to me.
If I was building a custom, I'd go with a 7 saum for sure.