So I have been getting 447 mhash/s on my 6970 using Phoenix with an optimized kernel. First you want to get the phoenix miner use the normal phoenix miner or the one that comes with the updated gui miner both work great. Here is a link for the normal phoenix miner! http://forum.bitcoin.org/index.php?topic=6458.0
Here is the link to the GUI Miner! http://forum.bitcoin.org/?topic=3878.0
. Once you have it downloaded install the custom kernel, but I assume you already have it... But anyways here is the amazing kernel that gives me +25 mhash if you guys are not using it you should use this optimized phatk Kernel works great. Here is the link for the optimized phatk kernel https://forum.bitcoin.org/index.php?topic=25135.0
replace the files in the gui miner with the new files in the rar from the optimized phatk kernel then you should be set. The next step is to overclock your 6970 as much as possible but make SURE you do +20% in the power options in the CCC in AMD overdrive to fix the really low mhash issues. Also try and get 1000 mhz if you can;t go that high try 950 or 970 980 990 whichever you can get stable you don't need to go above 1250 mV to get the 1000 mhz oc but if you can do it you should be fine I also find leaving the memory alone gives you the best results fi you go down to 600 or 300 or 188 you will see a loss in mhash for some reason I think it's not worth it. ENJOY!
Here is the screenshot of my mhash
AMD Overdrive +20% Power Tweak to avoid really low mhash.