I have a Sentry 10-gun safe I bought 3-4 years ago for $300 and change. It's great, though may be getting a little crowded :-0.
Whatever you do, don't believe that just because it's "on sale" or a "Black Friday" deal that it's actually cheaper than what you could get elsewhere. I recommend going to some search engine like the google shopping thing and search/sort by lowest price. For example, here's a search for my safe:
sentry safe 10-gun - Google Product Search
The biggest thing to remember if you buy online is that you will have to pay for freight shipping which isn't cheap. Also, if you have Costco nearby they sell a safe or two. For me, Wal-Mart wound up being the cheapest place selling my safe after shipping. Your mileage may vary.