Case: $55- Apervia X Dreamer(feel free to select any other in case you don't like this one)
Total (Excluding Rebates) : 1021 USD
Rebates: 80 USD
That should be of help.
Also about dual GPU i.e. Crossfire/SLI allows us to achieve performance of a costly single GPU by investing in two cheaper GPUs.
Example : GTX 460 SLI beat a single GTX 580
This card HIS 6950 has great ability to pair with another similar card to give exceptional gaming experience.
Proof : http://www.techpowerup.com/reviews/ASUS/Radeon_HD_6950_...
So when you have extra money in future get another of this card. You don't have to worry about power supply, 850 watts is sufficient for your needs