Have you considered the ATI cards?
If you need assistance purchasing I have dealership rights with various wholesalers in JHB and CPT.
For isntance, these prices are excluding VAT
EVGA GeForce GTX 560 Ti 1024MB (Free Performance Boost) - 256-bit, 850MHz Clock, 1024MB 256-bit GDDR5 Memory 4104MHz, 384 Cuda Cores, 2 x DVI-I Connector, 1 x Mini HDMI, PCIe 2.0, 3 Year Warranty R 2 295.00
Or
Club 3D Radeon HD 6950 2GB - 256-bit, 800MHz Clock, 2048MB 256-bit GDDR5 Memory 5000MHz, 1408 Stream Processing Units, 400MHz RAMDAC, 1 x Dual DL-DVI, 1 x HDMI , 2 x Mini Display Port, 2 Year Warranty R 2 195.00
If you're running a large display then I suggest a card with a decent ammount of ram for teh screen buffer.