There is a pretty good thread on this subject called "Changing Caliber with Savage" in this forum. Read it and it will help you with your decisions.
I was the one that came out of that topic amazed. I lost a lot of respect for the people at Savageshooters.com being knowledgeable over the topic of changing calibers on a Savage. I for one will not waste time on that site again.
Recently I kind of went through what you are talking about. I bought a 10fp in .223 for varmint hunting. For the ranges I'm shooting at the .223 just doesn't make it. So my decision was to rebarrel the rifle in .22-250. I was given prices on that site of $400 to convert to .22-250. Shoot, for $60 more I could buy another rifle.
If it weren't for the knowledgeable users on here I'd have sold the .223 yesterday. It was pointed out to me that you can do the conversion for $200. That in my opinion is cost effective.
I have all 3 of the calibers you mentioned, great cartridges and they have different uses. Not sure what I would do but I think the answer is to see what happens. If you find you have a need for a .308 but are still shooting the .223 buy another rifle.
