PV2 Newman,
I whipped up something pretty quick that has the best bang for your buck, but I did not include stuff like a computer tower, or storage since that depends on your current situation.
CPU - Since you are looking into streaming, recording, and rendering videos, an i7 intel CPU would be the best pick since the chip does have hyper threading and will cut down a considerable amount on render time. Also ArmA 3 is known to be CPU intensive and an i7 does work pretty well with ArmA. I recommend the
i7-7700k, since the next step down is a 6700k, and its only a dollar less at $333 with the current deal on amazon. It is also the unlocked version of the chip, so if you wish to get into overclocking later on you can do so.
CPU Cooler - Sort of a necessity since what we do in ArmA, I have not taken the trip into liquid coolers yet. I have the
Hyper 212 Evo and it has suited my needs for quite awhile now. Plus $25 dollars for a pretty decent cooler is okay for me.
Motherboard - Any
Z270 motherboard will be okay, you can find a decent one for $150 if you are looking to cut down on cost. I typically like to stick with ASUS or MSI on this pick, but that is my own preference. Plus you get to make good on that new-ish DDR4 ram, I haven't traveled down that road yet myself.
Memory - Since you have the Z270 motherboard, you need yourself some DDR4 ram. Maybe a year or two ago, the minimum you needed for gaming was 8GB, but today I feel as though 16GB is the new minimum. Luckily RAM is pretty cheap across the board, so the
G.Skill RipJaws V Series (16GB) is a decent pick.
GPU - This is the area I focused on bang for your buck. for $259 you can get a
GTX 1060 with 6GB of memory. If you wish you can move on up to a
GTX 1070 8GB for roughly $400.
PSU -
EVGA makes damn good power supply for $80, and at 650watts you allow yourself a little wiggle room when it comes to upgrading for the future.
What you can expect from this computer is one that is future proof. DDR4, the Z270 motherboard and the newish i7 I linked above are all still pretty new to the scene of gaming computers. The only thing that updates frequently is GPU's. Since graphics cards are getting cheaper and more efficient, we can probably look to more very cheap, but pretty badass graphics cards that are going to have constant releases. So that is what you can expect to update in the future.
As for storage, I recommend a SSD for your OS, and a WD Black for any gaming/video editing software. You can pick up a
WD Black 2TB for $120, and a
Samsung 850 Evo 250GB for $108. Both of which have awesome ratings.
I will leave the tower, mouse and keyboard to yourself since that is pretty subjective. However if you are looking to record, getting a crazy clicky mechanical keyboard will not be a good option unless you buy
O-Ring dampeners for all your keys.
If you are looking for a video to learn your assembly process,
JayzTwoCents has a few tutorials on building a PC.
