My model is W0163 and it has 3x 6-pin PCIe connectors - every Radeon 5870 card requires two 6-pin PCIe connectors.
I was told on a different thread that there are MOLEX-to-6pin-PCIe cables to use for that purpose though.
I've the same model, though I want to crossfire twp 5770's, not the 5870.
Having said that, the W0163 has
1 x native 8-pin
2 x 6-pin connectors
1 x 8-pin --> 6-pin connector
So you essentially have three 6-pin connectors (the 5770 only needs one) so for the 5870 all you'd need is one more 8-pin --> 6-pin connector.