Just to touch a up a bit more about this the Geforce 8800 Ultra is about 60% more in performance vs your AMD Radeon 7450. The 4870 is about 77% more than your card. You also have to factor in the other components on your system as well. So could you run it perhaps in the very low settings. It would be lower than what the PS4 and the Xbox One will do. If all else fails and you can't run it. IF you preordered from Origin you can get your money back.
From Origin's Great Game Guarantee:
EA games purchased on Origin qualify for the Great Game Guarantee. If you don’t love it, return it!
You may return EA full game digital downloads (PC/Mac) purchased on Origin for a full refund within 24 hours after you first launch the game, within seven days from your date of purchase or within seven days from the game's release date if you pre-ordered, whichever comes first.