It's a bit of a round-about way, but there's also a few Incarnum melds that'll increase it. Take the Shape Soulmeld feat and get either Beast Tamer's Circlet (+2 Insight Bonus to Handle Animal and Wild Empathy checks) or Unicorn Horn (+2 Competence bonus to Move Silently and Wild Empathy checks). A lot of DM's dont accept Incarnum though so it might not apply in your case.