What do I need to buy? Please Help?

Hi, I am new to the whole Digital world of DJing and am really interested as purchasing Mixvibes.
I have 2 CDJ400's, a DJM700 and a Macbook Pro running Snow Leopard.
I am imagining I need to buy the Mix Vibes Software which is available on http://store.Apple.com/uk-edu/product/TW885ZM/A
1. Do i need to buy the Cross Pack with the user interface U46MK2 though or would the software on its own be okay?
2. Also are there any compatibility issues with Snow Leopard?
3. Can I then use 2 channels on the mixer for use with the laptop and 2 channels on the mixer for use with the CDJ's?
I have 2 CDJ400's, a DJM700 and a Macbook Pro running Snow Leopard.
I am imagining I need to buy the Mix Vibes Software which is available on http://store.Apple.com/uk-edu/product/TW885ZM/A
1. Do i need to buy the Cross Pack with the user interface U46MK2 though or would the software on its own be okay?
2. Also are there any compatibility issues with Snow Leopard?
3. Can I then use 2 channels on the mixer for use with the laptop and 2 channels on the mixer for use with the CDJ's?