Not sure if you've already done it, but.....
Restrict your CPU to six cores (in the client and using something like Bills Process Manager) and dedicate the remaing two to the GPU's (using Bills Process Manager - use two HT Cores for the GPU's).
I've found using GPUTracker for the CPU and FAHControl for the GPU's works better - this way the CPU should get between 18k to 20k and the GPU's should get 25k to 26k (not the best wu's available for the GPU's atm but the better wu's will increase the GPU's ppd upto around 35k).
Also, maybe better if you run your rig without the side panel off and manually set the GPU Fan's (EVGA Precisionx or MSI Afterburner) to run at 90% at around 70c (trial and error with this to find a happy medium).
My 670's (oc'd) are currently averaging around 28k on the 807x's and the 3770k (oc'd to 4.7GHz - Noctua D14 with temps at 60c) is averaging 24.6k on the 6981's.
Is the memory clock important for folding? I was under the impression that other wasn't.
Very Nice
Almost as good as my 680's but at a lot less cost.
My 680's on the same wu's are averaging just over 42k across all four.
The rig is running around 192.5k PPD
Are you using the Client-type 'advanced' flag or 'beta' flag?
BTW: best keep an eye on the GPU's - those WU's become very unstable with high OC's
Also, what make/model are your 670's and what core speed are they running at? (I will check mine in about an hour and let you know what they are in.c speeds)
have yiu increased the power usage to the highest setting?
That is if I ever get time..... Turns out nuclear submarines can occupy a serious amount of time