If you are using external usb graphics either by using standard adapters or docking stations, the DisplayLink chipset allows you to configure up to 6 displays. Note that performance on the displays depends a lot of the GPU you use and what applications you want to use. In this case if you choose this method, adding your existing video ports you can figure how many displays you can obtain.
In regards to using the MST Hub we don’t recommended with the Intel 4400 as we have tested this GPU on a standard desktop configuration as well as the Intel NUC and we are not able to drive individual displays or MST Mode, only on SST mode (single resolution across several displays only). On the other hand on the Intel HD 5000 series we did not have any problems.