So one thing I had to work through was that not all chips are made the same. they cant ALL hit 650Mhz, its overclocked after all.  For my personal rig, I start with a single stick and work that up to as high as I can slowly tweaking over days at a time, most (but not all) can get to 600 Mhz stable. I take a magic marker and write the max hashrate on the side and set it off for later use. do this with each stick you want in your rig till they are all done. You can either then run multiple cgminers targeting the individual sticks, or just a single copy, set the to the max frequency of your lowest unit. (the second is what I do, I'm to lazy to deal with multiple copies).

Watch your USB hub too, the plugable your running on should be able to run 4 at 600Mhz before it maxes out the power, but that's if they all are running at top efficiency and cooled perfectly.