This is the system I have built for my children and as a NAS.
It's an unraid system mounted in an old cupboard to the wall, its still a work in progress but does well enough to run both of them and stay cool.

Stats:
Cpu: i7 4790k Delided Overclocked to 4.7ghz
Ramm: 24gb DDR3 Kingston Hyper X 1333 Overclocked to 1600mhz
Motherboard: ASUS Maximus II
Video Cards: Gtx 680 Overclocked 160Mhz
Gtx 660ti Overclocked 110Mhz
HDDs: 6x Western digital Green 2TB
120gb Samsung EVO SSD
Cooling: Custom water cooling loop D5 pump and 480x30 Rad, clear res
10X 120mm fans