While Hyperdimension Neptunia and Ar Tonelico Qoga: Knell of Ar Ciel have specific dates in Europe, all we have in North America are vague "spring" timelines for those titles. Nevertheless, Gamefly claims to know the dates of both games.
According to the rental service, Hyperdimension Neptunia is slated for February 17. That date is inline with the "few weeks prior" comment from NIS America. Ar Tonelico Qoga is pegged for March 17, which is also a little earlier than the European release.
In addition to these titles, NIS America also has Prinny 2: Dawn of Operation Panties, Dood! and Phantom Brave: The Hermuda Triangle coming out for PSP next year.