There is a big difference between 111MHASH and 100MHASH. Play with --kernel, --xintensity, --lock-cclock, --lock-mclock and power limit to tune the rig. Perhaps you can get all the cards to run faster than 108 MHASH with some more tweaking?.. I had a user on reddit who bought a new PSU and gained a few MHASH'es. More power, but +10% more money in the pocket might be worth it...
The memory speeds range all the way from 10180 to 11240 as you can see, thereof the different hashrates. All the cards are at their maximum memory speed.
