1. Your 250 GB SSD will fill up fast ....it starts off with just 232.83 GB of file space
2. Setting aside the recommended 15% free space leaves you with 197.9 GB of space ... figure Windows will be 80Gb within 6 months leaving you with 118 GB ... with today's AAA games running 30 - 65GB, doesn't leave you much room for games.
So all those other games will be sitting on that slow HD .... you wanna go w/ 9.76 MB/sec or 6.55 MB/sec ? I'd grab a SSHD for the 50% speed increase
http://pcpartpicker.com/part/seagate-internal-hard-drive-st1000dx001
http://www.tomshardware.com/charts/hdd-charts-2013/-17-PCMark-7-Gaming,2915.html
3. I can't see a case, outside of 4k resolution monitor, where I'd pick a 390 over a 970. If you uyse MSI afterburner, the 970 tops the 390 and 390x at 1080p and 1440p. See below
4. You have a 750 watter PSU which is too small for twin 390s .... it is big enough for two 970s tho. You'd want an 850 or better for twin 390s if the plan is to upgrade to a 2nd card at some point and extend system life by 18 - 24 months. If you are certain that will never happen, then you only need 600 watter,
5. The Colossus is a interesting looking case but I think it's aggressive styling may wear on you after a while..... however it is a well reviewed case. I'll offer one alternative to peek at before pulling the trigger:
Scoring = 97 / 98/ 96 / 95 / 96
http://www.tweaktown.com/reviews/3493/bitfenix_colossus_full_tower_chassis/index8.html
Scoring = 100 / 99/ 100 / 98 / 100
http://www.tweaktown.com/reviews/6574/phanteks-enthoo-luxe-full-tower-chassis-review/index8.html
6. I am concerned that the Asus Z-170 has some pretty poor ratings from Z170 board owners with 19% giving it a lowly 1 egg rating. In this price range, I like the Gigabyte G1 Gaming and the MSI Z170-A M5 offerings..
The big downer for me on the Asus, other than user satisfaction, is the budget ALC892 audio solution
$127
http://pcpartpicker.com/part/gigabyte-motherboard-gaz170xgaming3
$149
http://www.newegg.com/Product/Product.aspx?Item=N82E16813130873
7. The Hyper 212 is great budget cooler... emphasis on the work "budget". Might want to look at the Scythe offerings in the $50 range which compete with the $75 big boys.