Daman,
I have a friend that, many years ago, used his 25-06 for 30-40 woodchucks in the summer......not a lot of usage. He told her that since he wanted to use that rifle for pronghorn someday (never happened) that he needed to buy another chuck rifle SO HE WOULDN'T WEAR OUT THE BARREL ON THE 25-06!
At your ripe old age of 21, you need to be totally honest with your wife and totally realistic about your finances.....a new house, family and hobbies are all fine if you work as a team........does your wife get to spend $300 on her hobby, house or massages when you purchase the 45-70? Will it be her rifle to use or the '06? Or neither?
Yes, rifles, shotguns, reloading equipment and the shooting sports are wonderful and truly additive, but building a collection the wrong way will only have you admiring it as you write your monthly alimony/support check.
Not trying to be negative, just passing along what has worked for me and my wife of 40 yrs and my acquaintences who haven't been so lucky. Note: My wife was actually a big encourager when I hunted Africa a couple years ago.......but we are still discussing whether a second trip is in the future, if you know what I mean!
dmitch