There's lots of good information in this thread and others on this site to use to your advantage. I personally would have liked to buy a 10 gauge or thicker safe, but couldn't find one in my price range or weight limits. My goal was to find one large enough to grow with, and to not break the bank (or stairs). I also planned to put it in a closet, bolted down.
After searching and comparing for the last few months I decided on the Winchester TS-22-11 at Tractor Supply. Found it on sale for $599 and picked it up so no delivery charges. It has a 12 gauge body, 30 min @1400F fire rating, weighs in at 507-lbs, has (12) active 1-1/4" locking bolts, 5-spoke chromed steel handle, external hinges, LaGard Kaba-Mas metal cased e-lock, full door panel organizer, lifetime warranty, and pretty nice paint job. The say it's a 24 gun safe and has an internal volume of 14 cuft (easily enough for 8-10 rifles and 20-30 hanguns, with accessories).
Believe me when I say, nobody is getting this thing out of the basement without a winch and a bunch of pro-wrestlers. Because of my stairwell configuration I'll probably end up selling it with the house if I ever move...geez this thing was bear to get down there (a dolly won't even work). Anyways I'm bolting it down and putting it in a closet which should limit any would be thieves ability to knock it over and pry at it or swing a sledge hammer at it.
I know there are stronger more secure safes out there, but they cost and weigh a lot more too. Prior to this I was using a small Sentry Gun Cabinet just for keeping idle hands at bay. I'm pretty happy with my decision and would recommend this RSC to anyone in a similar financial and structural situation.