Re: 2 rifles...cxp2 and cxp3. What would you choose?
If you want a 2 rifle set, I would go 243, 257 Bob, or 260 for the light rifle, and 30-06 or 280 for the larger rifle. For up to 400 yards, a magnum is not needed IMHO. One rifle in 270, 7-08 or 308 would also do well for a lot of years.
It depends on whether or not you will be eating ammo shooting varmints as well. A smaller caliber makes more sense to me if that is the case. If you are only talking big game, I would just get one rifle and shoot lighter bullets until they are big enough for heavier ones.
I started with a 243, and for deer and antelope it was just fine with 100 grain bullets. When I started elk hunting, I used a 30-06 with 180's. We also used the 243's for varmints.