Regarding the 12 gauge versus the 20 gauge, if you're not going to do a lot of walking and therefore don't care too much about the weight, then the 12 gauge will give you a few more yards of range on the long shots...and if you're going to go into areas where there's grizzlies, it's best to have 12 gauge slugs in 3" shells than 20 gauge. If you ever have an issue with black bears, the slug from a 20 gauge will work just fine on them. I was going by your location in the West Koots, so I recommended the lighter shotguns in 20 gauge...especially if you're doing a lot of walking. The versatility of the over and under, with a barrel set up for long shots and one for close shots, is a nice bonus. If you decide to go for an 870 pump or Weatherby SA-08 semi-auto, two good choices in those actions for reasonable money, then use a modified choke and just change the shells depending on the distance of the game. I use a buttstock shell holder and put the light loads at the front and the heavy ones at the back, so there's no hesitation when it's time to shoot.