I made a test mining rig under 50k with the following components
Asus M5A95 USB 3 Motherboard
Corsair 4 GB DDR3 RAM
AMD 6300 FX ( You can opt for cheaper processor as well) I intend to game too on this one.
Corsair 650 Watt PSU
Cabinet with 5 fans low pressure system for cooling
Asus R9 270x DC2 2 GB ( Wanted 280x but that was not available at that time)
No Monitor (Connects to my home TV).
I get 400+khash at 18 Intensity @less than 72 degree C.
I would suggest go for 280x as these are available now and the total should not set you back by more than 60k. Also invest in a mother board with multiple pcie 16x slots for multiple cards if you don't want the hassles of riser cables.
Let me know if you need more details.