Marss I'm working on the same issue, I'm glad you found the optimal setup. Can you please a screenshot of your clock speeds and all of that? I'm really new and just bought 2x7970 so I'm not really sure where to set those speeds and screenshot would be extremely helpful.
Thanks
Keep in mind that the optimal setting is different for every card. I set my clock speeds at the cgminer command line. The full command would look like this:
cgminer -o pool.url -u user -p pass --gpu-powertune 20 --gpu-fan 0-100 --gpu-engine 1024 --gpu-memclock 1692 -I 13 -w 256 --thread-concurrency 8192 -g 2