I have to go with vapodog and the 35 whelen. I have a whelen that I use for my do-it-all general big game hunting. I can't think of a better round for moose. I use a 250gr Hornady RN and a 225gr Sierra SBT in my whelen. THe 250 @ 2400fps and the 225 @ 2650fps. I have my loads worked out so that I can use the same zero with both loads. The 250s will print nice little clover leafs at 100 yards dead on and the 225s hit about 3" higher. This puts the 225s dead out at around 250 yards and still holding on hair at 325 yards on a carabou.

Here in alaska almost all moose hunting is done at less than 300 yards. In the areas that I hunt most moose are killed at less than 150 yards. According to Federals online ballistic chart the 225gr whelen drops only 3.2" more at 300 yards as the 200gr 300 RUM load. The difference opens up to amost 10" at 400 yards. I guess if your planning on mostly 300-400 yard shots the RUM might be a theoretically better choice. For the extremely slight advantage in trajectory that the 300 RUM has over the 35 whelen, the whelen has a very distinct advantage over the 300 rum due to Recoil, muzzle blast, and magazine capacity.

The 338 win mag is another excellent round for moose hunting. It is practically identical to the 35 whelen ballisticly but is much more readily available. You can get 338 win mag ammo amost anywhere, especially here up north.

As has been stated earlier in this thread moose are not really that hard to kill and your 30/06 will do just fine for them at all practical hunting distances. I would look more to a rifle that fits you well and you can shoot accurately in any of the medium calibers.