Empty Quiver,
Your post asks all of the experienced people on this board to look at your list and tell you what is missing. And the majority of them are telling you the same thing. You have a big hole in the middle of your collection, and what is missing is either a .30-06 or a .308 Winchester, perhaps the two greatest mid-bore cartridges ever invented.
You repeatedly answer by saying that these cartridges can't do anything that your .300 Magnum won't do. I apologize for saying that you are incorrect. They will kill any deer, black bear or elk on the planet stone dead, out to 300 yards, with far far less muzzle blast, muzzle jump, muzzle flash, recoil, noise, powder and barrel length (and with factory ammo costing half as much) as a .300 Mag., and without blasting clean through the animal at moderate ranges.
Using your logic, you should throw away your .45-70, because there is absolutely nothing that a .45-70 can do that your .300 Mag won't do better.
Try shooting a box of your .300 Mags at the bench, and then switch rifles and shoot a box of .308 Winchester. I believe that from that point onward, you will always grab a .308 for your deer hunt.
Hope this helps. :-)
Mannyrock