Confused: How to go crossfire?

[t_aitch]

I have a Powercolour X1800XT 512mb softmodded to PE.

How would i go about going crossfire? Im kinda probing that route, and im a bit confused with all of the crossfire mastercards.

I see on the ocuk shop that they have a Powercolour X1800 Crossfire edition, but its over £300!! Is this a mastercard?

Is this what i need? or can i mix and match mine with other X1800 mastercards?

Someone needs to help me before my head implodes.

 

[t_aitch]

Yeah i thought that might be the case.

Seems a little expensive for me, i might just have to go for Sli then, seems much cheaper.