Help with CrossFire Setup

[NX1000]

I have an ATI X1900XTX and a mobo with AMD 580X CrossFire Chipset. What are my options for adding a CrossFire card? I know about the X1900CrossFire, but do I have to use a CrossFire Master or can I add a second ATI X1900XTX? Will a X1950 series work?

 

[heyheybooboo]

Combination Options Chart