I see some people advising a .25-06. I personally wouldn't go that route for two reasons:
1. Muzzle blast is pretty bad unless you get a 26" barrel.
2. You are are still limited to a pretty small bullet.
I know there are people here that are saying the .243 will down an elk quite well when hit in the proper vitals - even with the lighter 6mm bullet. That is true but this is a case where heavier really is better. I believe you stand a much better chance of a successfull shot if you can choose a caliber where the bullet is up in the 130+grn weight.