If you do get a 300 make sure you buy a minumum of 180 grain bullets for hunting, and they HAVE to be premium bullets to hold up to the impact velocity of a 300. On deer and such it isn't as big of a deal, but on large tough animals the bullet must be very well constructed to do it's job. The higher the velocity the harder it is for the bullet to stay together.
I would not recommend a 300 for a first rifle. Recoil and ammo costs make it a poor choice. I think the 30-06 is PLENTY of gun for moose, ammo is cheap and the lower recoil will allow enough practice to gain competence in its use.