This will be a mining-only rig.
Would like to be in the 750M - 1 Ghash range
A budget helps

My friend and I put together a 1.2 GHps rig for about $1100. No case, no hdd/optical. <$1 per MHash is very doable.
5850s, AMD quad, free RAM, and MSI 890FX board with 1 kW PSU. Should work well. Building tonight =)