In my newest rig, built ignoring power requirements and mainly most hashes for less $ I went 5850 and I get 300Mhash/s ea. I run 2x5850 in each box. Total of three boxes running on our datacenter floor. Total cost was about 340$/each using chassis mobo and CPUs I had. I het 5850s for 129$ from a vendor we do a great deal of volume with each month.