Welcome hoser,

As a former California resident, I feel your pain - go east young man!

I, on the other hand recommend the .30-06. The ammo is readily available and much cheeper than the 9.3x74R (and it's also readily available in tree-hugger friendly non-lead). I have several rifles in this caliber, including a side-by-side double, and for the shooting that we do most often out here in the rockies you are going to need a flat shooting bullet that will go the distance with little drop. Check the ballistics, and I'm sure you see that the .30-06 will be the weapon of choice.
One other item worth mentioning - I just recently took my first safari to Africa for plains game, and the PH recommended that I use my .30-06. I followed his advice and am so glad I did. Six animals were harvested, all at an average of 200+ yards; all one-shot kills. Go with the gun that's proved its worth of over 100 years...