Jason,
I have both a 20 and 12 gauge setup with scopes for deer. With the continued improvement of sabot ammunition you'll really like having a scoped gun. It takes a little getting use to. I recommend a 2.5 power scope with the longest eye relief you can find. I believe one of mine is 6 inches and the other is 5 inches. I just switched to a rifled barrel on the 12gauge and remington 3" copper solids. Very soft on the shoulder and extremely accurate. I've heard that Winchester has an even better sabot which is both faster and longer. On the 20 I shoot an improved cylinder choke and cheap ammo(remington sluggers). Very effective and a lot more affordable. Also a much lighter gun, less wear and tear both shooting and carrying. My 15 year old son carries the 20 most of the time we are hunting together. It is his preference.