Ninja gaiden sigma 2 new content?

I have ninja gaiden 2 and was a huge fan of it. I was wondering if anyone knows exactly what they have added to sigma 2? I know you can play as ayane rachel and momiji and that there is a new huge sword and musket for ryu but is that it? I know there are new boss fights and levels but how many of each? Basically all I want to know is if i should buy sigma 2.