In addition to what's already been said above I will just add that SGminer is pretty damn old now and that you can only extract that much performance out of those kernels.
There are newer, much better miners out there that have been developed from scratch that'll hash CN algos much faster than any SGminer fork will ever be able to do by now.
Examples? I have never found a miner faster than SGminer. Also none of the new miners fully support remote monitoring using JSON. Claymore at least had Ethman.
I primarily want a miner that has decent JSON, like CGminer has. The developer of SRBminer has said that their miner supports it, but I have not found info on it.