If you're in a hurry and the duct tape route is really what you're interested in, then I think this one will do and it's $20 lol (plus $5 shipping) http://www.evga.com/products/enlarge.asp?pn=112-CK-NF70-RX&I=1
Looks like it has a single pci-e x16 slot for one of your 5850's and it says it supports Core 2 quads :wink: the only problem could be the lack of ram slots. If you have 1GB modules, then 2GB total might not be enough. If you currently have 2GB modules, then 4GB total is all you need for gaming and you'll be golden.
link to b-stock page: http://www.evga.com/products/prodlist.asp?switch=20
well, i got tired of waiting for the other one, so i just ordered this. hopefully it will work. i do have 2gb ram modules, should be good to go.