I have a Safe full of long guns and always grab the M77 6.5mmSwede.

With what you have already, I would look for a 6.5x55.

go with either the 25WSSM or .257 Roberts
i would go with the roberts first because it can acheive velocities up to 5000 fps if handloaded correctly, also these are tack drives and all have pletny of velocity and energy

with all iv'e read the .243wssm is the best all around.my heart it set on the .240 wby.i don't think you can can go wrong with any of the cals.

25-06

Don't forget the .260 rem. Can't go wrong with the 243, 25-06, 6.5x55.

25-06, 264 win mag, 260 rem, or 6.5-284. all would fit your bill nicely.

.243 Win.

25-06,25-284,6mm-284,257 WBY,257 Rob,250 Sav.
My choice the 25-06 Rem
BBJ

223 rem mini 14
270 rem m77 and rem 7400

all threework great.