From what you explained.....and already having a .30-06, I'd say why get a .300 mag.....they'd be pretty close, and not give you more of a variety, so I'd suggest a .338 cartridge, long range, and power, so perfect for a sheep or elk, and you say you may not hunt grizzlies or africa, so no need for a .375 really, but you may hunt elk or sheep in griz country....or moose etc....therefore a .338 is pretty huge over a .300 IMO.

I'm a big fan of the faster .338's, there are really only 2 IMO, the .338 RUM and .340 WBY. I think the only RUM's that are doing well are clearly the .300RUM, with the .338RUM I think doing well as well, though not certain. The .375 RUM is dead as far as I know and so is the 7mm RUM, I wouldn't worry about buying a .300 RUM, but a .338 RUM might cause me a little concern.....

The .340wby does shoot a little faster, and will always be available...its also loaded from 200-250gr, the RUM only is loaded for 250 as far as I know, though you should probably stick to 225 or 250gr with either.

So may say ammo costs.....are a concern, but a .338RUM loaded with a premium bullet from say federal premium should be quite close to the .340 loaded. also I doubt you'll be shooting any magnum 300 or 338 alot.....so that extra 10-20bucks/box should be fairly insignifcant.

You can probably get a .338 RUM rifle cheaper than a .340 WBY, though you can get a WBY at a decent price, their MK V synthetic would probably be the cheapest, though I like the fibermark over the synthetic.

You could get a .375H&H, they now load that down with 250gr or 235gr bullets...etc.....and then if you did goto africa you could legally hunt anything.....and yo ucan find a cheaper .375 probably, ie a CZ though those prices are going up I think, due to the strength of the EURO, and ammo may be cheaper than say a .340 or .338 rum.

I'd strongly consider the .338 RUM or .340 Wby., not a .338 win mag, if that's what you're leaning towards I'd then say just get a .300 RUM.

I'd stay away from a fixed 12x scope, this won't be a target rifle, and something may pop up at 25yds.....with a 12x you may never see the animal! get a 4-12x, they're not hard to adjust......leave it on 4x when stalking, crank it to 12x when shooting 500yds....

the .300 win mag to me is close to the .30-06 IMO. I'd consider a .300 RUM or .300 WBY, if you decide against the .338 RUM or .340 wby. I'd avoid the .300 win mag, and .338 win mag.

Though the only choices IMO would be which .338, the RUM, or the WBY? or maybe a .375H&H.