also keep in mind, if you're only playing on 1080p and want to save a bit of cash, keep the GTX 1060 in mind, although it's the "lower end" card in theory that thing still seriously packs a punch 
i've built many gaming desktops in the past on a budget and it all comes down to what you need it to do, seeing as you play ARMA 3 and such a strong CPU such as the 6600k is a great choice, plus with adequate cooling, overclocking becomes an option to either keep the CPU going strong years later when that performance boost is needed or if you want better FPS in the here and now. For this to be the case the motherboard is something you want to splurge on a little to be able to make sure that if and when you do overclock, you've got the right parts to do so with, generally on a cheaper build i would recommend going for a cheaper motherboard as it will save you money and effectively give the same result but in this scenario (if you choose to overclock) a higher quality board will be needed. 16gb of ram is becoming the norm these days and i mean it's ram.... so long as it's DDR4 you can't go wrong, The drives are again something you can opt to change if wanting to slim down the price again. a 500gb sata drive is somewhat excesive, in reality a 240gb would be enough, you only want the important stuff on it as having too much data on an SSD will slow it down, so you only really want vital programs, you're operating system and perhaps a game or 2 that will benefit from the faster read and write of an SSD, the 2tb drive is a definite as more and more goes digital the minimun for storage has as well, I personally have 2tb and that's full of games, this is only on the one PC, i have a few others storing the rest of my games, music, movies etc. the power supply is a great choice, 80+ bronze rating is a great thing to have on your PSU and EVGA is a real great brand and lastly the case, for the most part, the case is something that comes down to personal preference, most all cases function the same and will ultimately do the same job, so again here you could opt for a cheaper case to save money or shop around for something that either looks nice to you or suits your needs a little better. As i stated above building a desktop all ways comes back to what you're doing with it, there's no point putting and i7 in a word processing machine and no reason to run a quadro in a gaming rig, every part has it's purpose, Hopefully this helps you make up your mind, also if anything i'd recommend doing your own research and learning this stuff for yourself, it's a lot of fun and rewarding in the long run knowing you built it yourself, nothing like the satisfaction of putting it all together, hitting that power button and seeing it all come to life .
i've built many gaming desktops in the past on a budget and it all comes down to what you need it to do, seeing as you play ARMA 3 and such a strong CPU such as the 6600k is a great choice, plus with adequate cooling, overclocking becomes an option to either keep the CPU going strong years later when that performance boost is needed or if you want better FPS in the here and now. For this to be the case the motherboard is something you want to splurge on a little to be able to make sure that if and when you do overclock, you've got the right parts to do so with, generally on a cheaper build i would recommend going for a cheaper motherboard as it will save you money and effectively give the same result but in this scenario (if you choose to overclock) a higher quality board will be needed. 16gb of ram is becoming the norm these days and i mean it's ram.... so long as it's DDR4 you can't go wrong, The drives are again something you can opt to change if wanting to slim down the price again. a 500gb sata drive is somewhat excesive, in reality a 240gb would be enough, you only want the important stuff on it as having too much data on an SSD will slow it down, so you only really want vital programs, you're operating system and perhaps a game or 2 that will benefit from the faster read and write of an SSD, the 2tb drive is a definite as more and more goes digital the minimun for storage has as well, I personally have 2tb and that's full of games, this is only on the one PC, i have a few others storing the rest of my games, music, movies etc. the power supply is a great choice, 80+ bronze rating is a great thing to have on your PSU and EVGA is a real great brand and lastly the case, for the most part, the case is something that comes down to personal preference, most all cases function the same and will ultimately do the same job, so again here you could opt for a cheaper case to save money or shop around for something that either looks nice to you or suits your needs a little better. As i stated above building a desktop all ways comes back to what you're doing with it, there's no point putting and i7 in a word processing machine and no reason to run a quadro in a gaming rig, every part has it's purpose, Hopefully this helps you make up your mind, also if anything i'd recommend doing your own research and learning this stuff for yourself, it's a lot of fun and rewarding in the long run knowing you built it yourself, nothing like the satisfaction of putting it all together, hitting that power button and seeing it all come to life .