"and almost without exception, their first choice for chambering was a 600NE"

Mac, you and I must hang out in different circles! That having been said, 600 doubles are sufficiently rare (and expensive) that there isn't much danger of a new guy buying one until the has throughly sucumbed to the DR bug.

I agree that the 9.3X74R would make a great first caliber. Not so powerful as to be intimidating, not too expensive for a decent 'shooter' quailty gun, and is suited for scoping for those who are transitioning from scoped bolt guns. I think the 375 flanged would be even better (more familiar to most in US) if ammo and brass were readliy available.

After that, I'd say 450/400. A classic caliber but a bit more powder/recoil than some deer/occasional elk hunters may be used to.

And finally, I agree with Tinker that a 22 DR would be and awesome set up! I acquired an Italian 410 a few months back with just such a project in mind, but have been waffling between a 22 Hornet and 22 WRM (with the attendant firing pin work).