Think about where it is going to go before you pick one out. It really does need to be anchored to the house unless you are buying one that is just too dang heavy for two or three people to move.
Buy one that is bigger than you think you need, they never hold as many guns as they advertise and you will probably add more to your collection, everybody does.
With those things in mind whatever you are thinking of spending now, save up and spend about double that. You are gonna want to buy the heaviest safe you can find. good luck