Hey bro,
Looks like two of these since there are only two x16 slots: http://www.amazon.com/exec/obidos/ASIN/B001RBE7GO/ref=nosim/7240466-rg2304-00-20?s=merchant
The thing that scares me is as stated above, if one of these cards goes bad, I'm down 4 monitors. Btw, with this setup, 8...