Your 308 is plenty for the bear hunt so no real need to invest in a new gun just for that adventure. However adding a new piece is always a good thing if you have the allocation...lol!! So may I ask what you hunt now? What you'll want to hunt in the future??

If deer sized mainy then why not look to diversifing your choices, seeing you have 30 cals already! Maybe a 2506, 270, 7mm 08, etc

If you are interested in pursuing elk, moose then 300 wm, 300wsm, 7mm rem mag, etc. Or add the chance ofmaybe even actually go on a big bear hunt griz or browns then 338 wm would be perfect for all of these critters.

Maybe poping paper/varmits is of interest look at 22 250, 223, etc. Or poping paper and small game at 100 plus look at .17hmr!

A host of possibilities but IMHO buying a 3006 isn't really going to do much more than the 308 you already got! Well unless you don't want to use the handed down piece much in the field...then getting the 06' would be understandable.