I love cat decks and I really appreciate the devotion to the cat tribal aspect. As fro suggestions, maybe Healer of the Pride somewhere to augment the sisters?

Thanks, UpsetTomcat, I'm glad you like it. I did consider Healer of the Pride but it's just too expensive at 4 mana; I'd have to increase the land count to be able to support it and it'll usually hit the battlefield after I've played the rest of my hand, which means it just won't have very many opportunities to trigger.

Qasali Ambusher perhaps?

I don't think I can use its flash ability consistently enough with my current mana-base; I've only got 5 Forests in the deck. I'll bear it in mind if I ever reach the point where I can afford a proper Savannah/Windswept Heath mana-base though. Thanks for the suggestion, Unlife.