[reginalb]

   
OK, I mentioned this because of no mention how you have got those plots.
 
Yes, it's easy to check if there's something wrong in filter bandwidth setting ... just use one frequency band (1kHz or close) and higher gain values than what you have mentioned earlier ... like maximum -/+ dB values then plot the response for few Q values (0.1, 0.5, 1, 2, 4). If response curve in plot remains same for all of the Q values then it's broken (dunno the implementation they used).
 
BTW, does the equalizer work for the headphones connected directly into AK300?

 
EQ works for headphones, changing the Q value does not, but changing the levels at various frequencies does work for headphones.