My definition of enough gun is a cartridge chambering capable to get to the "goodies" (vitals/CNS) even from odd angles at the intended distances
H&H I hope the admin dos not lock the thread because of my reply to your points.
Actually I heard from quite a few people that lived in Alaska or are still in Alaska that an -06 with the right bullet is plenty medicine, tundra or coastal.
There is a joke that says that the caliber required to kill a big grizzly it gets bigger as you getting closer to Anchorage
Some of these people have seen big brownie more than some guides.
Some actually prefer for defence an easy handling and loading rifle (a lever 45-70, a pump 12 gauge with slugs or a pump action Remington in 30-06)
Caribou has taken a quite remarkable big one (inland or coastal it was big regardless) when he posted his pictures and he did with a bullet weight that many would not consider ideal... FMJ 147 gr. light weight, non expanding.
A 1951 Kodiak Bear hunt record....1400 pound...rifle a Winchester boltie in 30-06
http://www.youtube.com/watch?v=b0diBlYy1H0
A 9' 6" grizzly taken a 80 yeards (pass through) with a 30-06 by a 17 years old
http://www.youtube.com/watch?v=B4HfhF4Rv5Q
Outdoor Life article "30-06: The Ultimate Grizzly Cartridge"
"“Anyone who says the .30-06 is not effective on brown bears or grizzlies either has never used one or is unwittingly commenting on their marksmanship.”
—An Alaskan Bear Guide"
http://www.outdoorlife.com/node/1001308838
That said, obviouly if you lke your 375 and you can fire it as easily there is no reason for you to use an -06