In my mind, the ideal moose rifle is a .35 Whelen. Good substitutes include the .338 cals and the .375 H&H. You can certainly kill moose with a .270 or .30-06 but you' d not buy those guns specifically for that purpose.

If you already own a .30-06, buy some 180-200 grain premium ammo from Federal and go Moose hunting....you have enough gun right now.