Boyd,
IMO, you are seriously handicapping yourself by not being a handloader. Especially given these two considerations. At the present time, I own 3 rifles chambered in .358 Win and two in 9.3x57.
Factory fodder is not exactly common in either chambering. Winchester being the only manufacturer of the .358. And Norma being the only maker of the 9.3x57. (Altho' Sellier & Belloit may make the 9.3, but I've never seen it...)
Personally I would not even
CONSIDER either one unless I intended to handload. I believe if you want a chambering of that power category, you'd be better served by the .35 Whelen.
Even tho' it's fun to be the only one around with an exotic chambering, It's pretty much useless without access to ammo...
YMMV.
Grasshopper