Dunno why a Quadro for general purpose desktop? Just get a cheap video card...
Do you need an optical drive? I took them out of all of my PC's at home and at work. Complete waste of space these days.
Also I'd go for 2X16GB dimms right off the bat. This makes for easy upgrading later to 64GB if needed otherwise you're stuck with 32GB max unless you toss your original sticks.
For cases I'd check out the Fractal Design R5 or Define S if you want something really nice for the price and sound conscience.
the i7 6700k is not really faster than an i7 4790k, the only thing what is better is the Processor Graphics, which is an Intel® HD Graphics 530 the i7 4790k has only an Intel HD Graphics 4600. So he wasted money. If he want focusing on streaming, he would still need a cpu with more Cores, like one of the 5k series.
Nope. 6700K > 4790K and both are quad core. Of course a 6 core will win in certain scenarios where more cores trump clockspeed and speed per clock, I went over this with him when he purchased and for his workload the 6700K will be more beneficial than a hex.
This from the guy that paid extra for the Founders Edition 1080 and then said its useless to overclock anything lol. Go back to your stream dude...
Now time for a high refresh rate Gsync monitor. I upgraded from the same Asus you have to a new PG279Q and the difference is pretty staggering. 165Hz , IPS, and Gsync is just, uhhhhhhhh spluge.
6700K is newer, slightly faster, and on a newer platform. No reason at all to go 4790K unless you have a bunch of DDR3 sitting around and want to save the money spent on DDR4.