Roger is right on the 490 mast.
If you are looking for a light wind sail, do not restrict your choice by your 460 mast.
You may want to check the mast curve of your powerex to see if it is compatible with the NP sail you are considering. Most NP sails don't rig well on other brands' masts.
However, $400 more for a NP sail? NP sails are overpriced ! Use the money for another mast.