The 4890 would be powerful but it does not support newer technologies like DX11, OpenCL (possibly), DirectCompute, etc. The 5xxx series do, and if you want a card that will last a long time you would be much better off buying a card that has these technologies. I would recommend a 5770, 5830, 5850, or 5870 (or 5890 which is 5870x2 basically), as these cards are ATi's latest models that support DX11/OpenCL/etc.