My avice is to base decision on how interested you are in hunting vs. plinking. A 30.06 Spr. is not usually considered to be an ideal "plinking" round, though I have hand loaded some 110 gr. bullets in a 30.06 case and way back when, some of the "accelerator" stuff.

If you expect to be leaning more towards the hunting arena rather that hitting 4" diameter targets at 400 yards, you will be well served by a top end Leupold variable such as a 1.5-6 x 40mm or 3-9 x 50 mm. I'd suggest a heavy plex such as a German #4 or German #8. I find it quicker to get on target with such a reticle, especially when light is very low.

Now ... if you are leaning more towards blasting soda can sized targets at 400-500 yards, I'd lean more towards Sheridan's advice. Something in the 10X-15X range. But such a high power scope is going to be a disadvantage in a short range hunting situation. Just not enough field of view at close range for me.