You specifically asked if you could connect a 2560*1440 120Hz monitor and I specifically answered this question. Yes, you can connect this monitor, but there is absolutely no way that it can run at the monitor's (implied) 120Hz frequency capability.
If you are still confused, let me state it another way: If you connect this monitor, yes, it's going to work, but the best that you are going to be able to do is 2560*1440@60Hz. That is, you can support this resolution, but only at a frequency of 60Hz. If running at 120Hz is an absolute requirement, then you are going to have to configure for this monitor to run at a lower resolution. Now, to be absolutely clear, you do not actually configure the monitor to run at a lower configuration, you configure the DisplayPort, within Windows (or Linux, or whatever other O/S you might be using), to utilize a lower resolution and the connection will be made at whatever frequency can be achieved.
Note that I very carefully crafted that last sentence to point out something important: The DisplayPort's max. resolution and frequency (i.e., 2560*1440@120Hz) is dependent upon a number of factors, the most important being the quality of the cable that is used to connect the monitor to the PC. In my experience, the cables provided by the monitor vendors are usually absolute crap, the cheapest that the vendors can get away with (they want to check the box saying that they provide a cable, but they do not want to pay a lot of money for the cable that they include). I automatically discard these cables (yes, directly into the recycle bin). I do not want to fight with connection and resolution/frequency issues. Bottom line, I recommend purchasing quality cables.
Clear as mud?
...S
