You have a 7mm Rem Mag and want a hard hitting calibre ? the 7mm you have is considered on of the best all round flat shooting hard hitting calibre going, I have a heavy barrel Rem 700 in 7mm Rem Mag there is nothing down here it won't kill at long range, the 308W, 270W, or 30:06 can't compete seriously with the 7mm Rem Mag ballistics, given that all other variables are equal, I'd choose a 7mm any time.
Unless your hunting rhino or elephants (both illegal anyway) the 7mm will drop most anything on the planet to quite long distance including your bears.
I have 4 rifles which is about all I will ever need, 22, 222 Rem, 25:06 AI, and the 7mm Rem Mag, the 7mm will drop our water buffalo or wild pigs at +250m without any problems.
If the 7mm don't rock your boat, try 338 Lapua Mag or kick some serious butt with a Barret 50 BMG