760 sli or r9 280x xfire

firo40

Splendid
I'd always say take sli over crossfire. If it was a 290 or higher that supported crossfire on the pcie bus instead of the bridge then I'd recommend crossfire. Take the 760's in this situation. Have you considered one good card over a multi GPU setup?
 
760's SLI looks better but I would go for system with single powerful GPU like this.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor ($209.99 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($35.98 @ Newegg)
Motherboard: ASRock Z87 Extreme4 ATX LGA1150 Motherboard ($119.99 @ Newegg)
Memory: G.Skill Sniper Series 8GB (2 x 4GB) DDR3-1866 Memory ($79.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($56.98 @ OutletPC)
Video Card: EVGA GeForce GTX 780 3GB Superclocked ACX Video Card ($499.99 @ NCIX US)
Case: NZXT Phantom 410 (Black) ATX Mid Tower Case ($79.99 @ NCIX US)
Power Supply: Antec HCG M 750W 80+ Bronze Certified Semi-Modular ATX Power Supply ($69.99 @ NCIX US)
Optical Drive: LG GH24NSB0 DVD/CD Writer ($14.99 @ Newegg)
Total: $1152.89
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-04-26 14:28 EDT-0400)
 

firo40

Splendid
A single powerful GPU is always better in the end especially in frame time variance and compatibility. Lots of gamed don't support multiple GPUs and if they do its down the road when drivers are released for it. Take a 780 or 780 ti