4x Asus EAH6870 cards here

only using ATI control panel, GPU at 1015Mhz, mem at 1100 (in ATI control panel)
getting solid 305MH/s connected to btcguild.com

guiminer w/ phoenix flags -k phatk vectors bfi_int aggression=10 fastloop=false

no bios mods, overvolting, or reflashing