Need advice for a crossfire

[Tudorel Luca]

Hi guys, first of all I'd like to let you know that I'm not that good with this kind of stuff, I do know some things, but not enough to make a decision.

So, this is my rig :
AMD FX 9590 Black Edition 8 Core OEM Processor 5GHz - H80 Cooled

Gigabyte GA-970A-UD3P AMD Socket AM3+ Motherboard
Corsair Memory 16GB DDR3 PC3-12800 (1600MHz)
XFX HD 7990 AMD Radeon Graphics Card 6GB
Aerocool X-Predator X3 Avenger Edition Red Large Tower Case
Aerocool Templarius Imperator 1150W PSU 80+ GOLD
Seagate ST2000DX001 2TB Desktop SSHD Hybrid 3.5" SSD 7200rpm

My questions are : What changes do i have to do to my pc to put another 7990 on it ?
Can i put as the 2nd card a r9 290x?

My budget is limited, so i would prefer to not make any changes if it's possible.

Thank you very much in advance !

 

[17seconds]

Crossfired dual 7990's was covered in a very infamous Tom's Hardware article:

Radeon HD 7990 In CrossFire: The Red Wedding Of Graphics
http://www.tomshardware.com/reviews/radeon-hd-7990-crossfire-overheat,3539.html

The setup has come very specific requirements in terms of case cooling and power. Pay close attention to the official AMD specs and you should be able to get it working. Good luck!