Like Pigoo3 mentioned, really need to know the model.
I will go out on a limb here and point out the current (late 2012) model will support two monitors. One via HDMI and the other via the Display Port. I will say I do not recommend using adapter/ gender changers for your cables. What I have and use is a HDMI to DVI cable and a Display Port (thunderbolt) to DVI cable for my two Samsung LED displays.
USB will not work to display. Not sure if the Thunderbolt/Display port in the 2012 Mac Mini actually will let you pipe your video and data over the same cable, for example running it to a thunderbolt storage and then to your display. I may be incorrect here, but I believe I did read something about it being a poor implementation of thunderbolt. The newer devices from 2013 and onwards should not have this problem. But like I said, I may be wrong on this and you very weal may be able to use both over that port on the 2012 model..
Just like to point out I use two WD MyBook USB3.0 drives and they clock in at 130MB/s, which is almost 35MB/s faster then the 1TB internal factory drive that came in the system. Just incase your considering other storage solutions.
Hoep this helps..