Cardboardkiller,

You are moving to Kansas, wide open spaces and the home of "flat shooting" rifles.
You have a 300 Ultra Mag., that will probably take care of the elk, moose, etc. if any such trip comes up.
You are buying a varmit rifle (22-250 etc.), that will certainly take care of the lower end.

Based even just on caliber spacing alone:
I would go with the 270Win hands down to "fill in" that middle ground.

Of course this is just my recommendation to Cardboardkiller who has both the 270 and 280 and neither has "won his heart". This is not an attack on 280 lovers anywhere. JMHO for a Kansas boy that already possesses a "big stick" gun.

Good Luck and Good Hunting,
EKM