If you're already gonna have a shotgun, I'd go with the AR.
James is correct, the insurance is a good option. I pay an extra $25/year for $5000 worth of insurance for my guns. That protects them from theft. In the case of fire, flood, etc, they are covered 100% anyway.
You mentioned an apartment. I live in a 2nd floor apartment, and I just got one of these safes. http://www.academy.com/index.php?page=content&target=products/outdoors/hunting/firearm_safes&start=8&selectedSKU=0340-03031-4311
They are not fire rated, but it will keep the common thief from walking aout with them. It's actually a pretty nice safe, and the price is great.
The safe weighs about 200 pounds, but it was pretty easy getting up the stairs with a dolly.