Looks good, if you are going to be playing ARMA lots though I recommend using more RAM, also with regards to cooling, liquid cooling is good but you will need to make sure you have a good air flow through the computer with a couple decent fans. You'll want that especially if you plan to overclock. Idk about the RAM make you are getting but Corsair is a good make. Graphics cards aren't necessarily majorly important if just for ARMA, a GTX 970 will do you as a solid card and save you 300 dollars, depends if you want to future-proof your PC and how much you wanna spend. The power supply is probably a bit overkill also. Other than that, good specs
Edit: As Ajax said, a small Samsung SSD is also a good shout just to boot up your PC super quick, but not necessary. For the price you can get them for and how much you are spending I'd say it's worth it.