I'm not familiar with that brand of safe. Safes are like a lot of things, you have to buy what works best for you. I myself would choose a safe that is strong enough that it takes time for a thief to break into, hopefully discouraging theft. I don't necessarily want everything in the safe to survive a 12 hour fire and those are much bigger and more expensive. Safes are like tents, they never comfortably hold as many guns as they claim they will. I would buy a safe with about double the capacity you think you might need, strong enough that it can't be easily broken into, and heavy enough that it takes more than two guys to carry out of the house.
As for just a key, I would have a digital keypad, you can hide the key somewhere else, but if the batteries die you can still get into it by popping off the keypad.