I think the 30-06 is perfectly capable of the shot, but I would personally feel more comfortable with a 300 magnum of some type. I'd stay with the 180gr bullet. I choose my cartridges and bullet based on what is perceived as the "optimal impact velocity" for that particular bullet. A nice, handy 30-06 with a 22 or even 24 inch barrel is great in the woods where shots will be between 50 and 150 yards. At those ranges, a 180gr Nosler Partition opens up reliably and penetrates at 30-06 velocity.
If ranges are beyond that, I'm assuming that the country is more open and a handy rifle isn't as necessary. For that, why not choose a 26 inch barreled 300 that pushes that same 180gr partition at velocities pushing 400 fps faster. That way, the same impact velocity at 150 from a 30-06 will occur further downrange with the 300. This will give you good, reliable expansion at the more distant ranges.
