Mark RM :
List the rest of your system specs please, in detail.
The minimum card I'd get is a GTX 1060, preferably a GTX 1070 or 1080 but the rest of your system needs to support such an upgrade
Motherboard: Gigabyte GA-990FXA-UD3 -- AMD 990FX w/ 4x PCI-E 2.0 x16
Processor: AMD FX-8320 CPU (8x 3.50GHz/8MB L3 Cache) Eight-Core Processor
Memory: 32 GB [8 GB x4] DDR3-1600 Memory Module - Corsair or Major Brand **FREE Upgrade to DDR3-1866 ADATA XPG V2**
Video Card: AMD Radeon R9 280 - 3GB - Single Card
Primary Hard Drive: 2 TB 7200RPM HARD DRIVE
Data Hard Drive: 1 TB HARD DRIVE -- 32M Cache, 7200 RPM, 6.0Gb/s - Single Drive