I went with a Champion "safe." (Whatever you want to call it.)
I've had it four years now, and did a fair amount of research before opting for something in the 1600-1800 price point.
The dealer I used rep'd multiple lines, and his basic take was that Liberty was his lower end, Champion the mid range, and AmSec the high end... Prices following that, too. He swaps out all electronic locks for S&G dials, although if you really wanted the electronic he'd do it, but warn you about it..
A good recommendation he provided is that if you're putting the safe in a place that might see moisture (like my basement) to put it up on four hockey pucks. Works well, and you can still tap a bolt in the back.
As someone points out, it's all about deterrents, and given enough time and tools, someone can get in. The dealer indicated a pretty common MO for theives is to rip off a concrete saw from a construction site, and cut in through the side. Even an AmSec is going to eventually fall.
Ultimately, for me, I kept in mind that I was looking to safeguard firearms, as well as some valuables. I already have an alarm system, so just getting in to the location of the safe is going to start the clock ticking. Moving a 1200lb object (empty) is going to slow them down, and it's not likely they'll penetrate the safe prior to the authorities arriving.
For fire protection, most modern safes of that tier use an expanding gasket material around the door that is heat activated, and is designed to seal off the safe from both heat and water in the event of a fire. At that point, you'd be working with the safe manufacturer to get it open... I do, however, use a secondary, insulated safe inside the primary to hold CD computer backups, important papers, etc. They also make "media coolers" and the like.
As another contributor pointed out, there is no real standard for measuring fire/heat protection, so I just wanted to have something that would last long enough that in the event of a fire, it was protected until the fire department came and hopefully got control of the fire...