I was in the same situation wile ago,I have Ruger#1 in 45-70.
My "mainrifle" is Sako 30-06,I hunt moose,also bear.I have taken down mooses with both..ok but the bear,I consider 30-06 light for bear...45-70 is singleshot..the day I face a bear, I want to have a strong hunting rifle in my hands,and the possibility for the second shot fast...if it needs. If I were you,I would take the Cz 550. I have now the Cz 550 in 375H&H cal,it took me long time to deside the caliber,even it was clear for me all the time,I went thru all alternatives,use,circumstances here..375 was my choise.Im sure I dont regret that.

Elias