Yeah, that should give you a bit of a boost. Be sure to benchmark your scores before and after, then weigh out if the boost is enough to justify the additional heat, noise, and power consumption of the extra card. Also make sure that your power supply is strong enough to handle two cards.
The PhysX in Plantetside 2 looks pretty awesome. There are a few more new titles on the way as well, including Batman Arkham Origins and the Witcher 3 with PhysX.