RE: 223 or 243
I am not sure if I am reading your post right, but it sounds to me like you are wanting to upgrade the quality of the rifle you have. So I am asuming you are going to get rid of the Savage. In that case I would buy another 223. If you are wanting to buy an additional rifle and keep your Savage then I would skip the 243 and get a more substantial cartridge.The 223 is adequate for what you want to do, but you are pretty much at the limit at 350 yards for ground hog's and coyote's. You might try the larger bulets-if you already have not done so.
I am not a fan of the 223 for deer.Some people like the 243 for deer, but I do not particularly care for it. Buy a good quality 223 now, and if you do some deer hunting down the road you can upgrade to a better cartridge and have two rifles. Tom.