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You might need a repeater with all of the concrete and steel. A repeater is cheap, effective, and will help you avoid dead zones that are common in commercial structures with steel/concrete construction. The AirPort Extreme is a very solid choice and may do the job fine, and if you do run into dead spots, you can just add on a repeater later.
If it was me though, I would probably just go with a Powerline Ethernet bridge, and a second wireless router located wherever you find any dead zones.