Anandtech measured the high end cards in a i7 Extreme Edition 4690X system. The system with a Titan X drew 392W while gaming, the R9 290X in Uber mode and the Fury X configur drew 408W.
http://www.anandtech.com/show/9059/t...an-x-review/16
Even nVidia's very conservative power estimates say the Titan X alone draws 250W and only recommend a 600W PSU for the system.
http://www.geforce.co.uk/hardware/de...specifications
Once you start to heavily overvolt the CPU then that can drive the power consumption up rapidly but on a mid-range cooler you're not likely to be that so I'd happily run the system on a 600W SFX PSU. The higher capacity PSUs are mostly four multi-card setups & serious overclockers, single high cards don't need much.
As to an alternative with a handle if you're not in any hurry then Silverstone's ML08 case should be coming out soon and looks very interesting. Similar height and depth to the Bitfenix Prodigy (38x37 vs. 40x36) but 8.5cm wide instead of 25cm.