However, that graphics card isn't going to be pushing 120fps at 1080p in any modern games unless you turn the settings way down, so it's not going to matter that you get a 120Hz monitor unless you plan at some point in the future to splurge on a $400 or so GPU.
Don't know what CPU You're getting, but you need a pretty decent CPU to pump out 120fps as well, as at high framerates you can often get CPU-bound.
I don't know about games, but I do see major difference between 60hz and 75hz doing even simply tasks like scrolling (makes it a lot more fluid), and moving stuff around.
May I make a recommendation? Thanks
If you want 120fps to really make a difference, you need a GPU SETUP to be able to push out a constant 120fps (preferably a minimum)...and thats not easy/cheap with new games at high resolutions. The card you linked to certainly won't pull over 120fps on high settings in new games.
If you want to make 120fps on a cheap setup, you'll have to sacrifice quality and resolution significantly, and that will suck.
Want a good gaming experience?...buy a plasma or an LED monitor. That will make a bigger difference than 120hz...either way your setup won't push 120fps so it doesn't matter.