Your thread concurrency is way too low. Try 25984.

Here is the cgminer.conf which gets all 3 of my 7950s up to 655kh all day long:

{
"pools" : [
    {
        "url" : "stratum+tcp://pool.pool.url:3333",
        "user" : "user",
        "pass" : "password"
    },
    {
        "url" : "stratum+tcp://pool.pool.url:3333",
        "user" : "user",
        "pass" : "password"
    }
]
,
"intensity" : "18,18,18",
"vectors" : "1,1,1",
"worksize" : "256,256,256",
"kernel" : "scrypt,scrypt,scrypt",
"lookup-gap" : "0,0,0",
"thread-concurrency" : "25984,25984,25984",
"shaders" : "0,0,0",
"gpu-engine" : "0-0,0-0,0-0",
"gpu-fan" : "0-85,0-85,0-85",
"gpu-memclock" : "0,0,0",
"gpu-memdiff" : "0,0,0",
"gpu-powertune" : "0,0,0",
"gpu-vddc" : "0.000,0.000,0.000",
"temp-cutoff" : "95,95,95",
"temp-overheat" : "85,85,85",
"temp-target" : "75,75,75",
"api-mcast-port" : "4028",
"api-port" : "4028",
"expiry" : "120",
"gpu-dyninterval" : "7",
"gpu-platform" : "0",
"gpu-threads" : "1",
"hotplug" : "5",
"log" : "5",
"no-pool-disable" : true,
"queue" : "1",
"scan-time" : "30",
"scrypt" : true,
"temp-hysteresis" : "3",
"shares" : "0",
"kernel-path" : "/usr/local/bin"
}