-k phatk2 VECTORS AGGRESSION=14
for dedicated mining or no monitor plugged into it. WORKSIZE is not specified because it's not needed. it'll default to the largest worksize your card can do. Dedicated cards for mining should be running 300-350MHz on the memory for this.
-k phatk2 VECTORS WORKSIZE=128 FASTLOOP=true AGGRESSION=4
for any video adaptors that you actively are on the PC for (internet browsing, gaming, etc). You should not need to adjust your memory speed for this (1000-1300+ MHz)
Now my question to you is how are you using guiminer on sdk 2.1? with 2.1, guiminer for me won't find -any- adaptors. Are you sure you're using 2.1? double check with gpu caps program. 11.8 driver comes with 2.5 sdk.
I'm using 2.1 and if guiminer doesn't work anymore, that's terrible because the old version used to work for me
I now prefer cgminer, it's almost like a gui, lol