The phrase "extra firepower" means having additional or more powerful weapons. It refers to the ability to quickly and effectively defeat enemies or overcome obstacles by having more weapons or stronger ones. Full definition
It is an open secret both in England and on the Continent that the Gunners are desperately searching for extra firepower in attack during the January transfer window in order to boost their chances of yet again qualifying for Europe's premier club competition, the Uefa Champions League, come the summer. (fanatix.com)
You can grow up to three heads for extra firepower, and there are a lot of power - ups, including a few transformations into other types of dragons with different abilities. (nintendoworldreport.com)
With gameplay taking place of three rounds, losers are bolstered with extra firepower and winners have to strike a balance between holding their position and retreating into greater cover. (stuff.tv)