If I recall, they have to be exactly identical cards in order for SLI to work. If you currently have a Gigabyte 570 GTX, you'll need another Gigabyte 570 GTX in order to SLI. In addition, you'll also need a power supply big enough to handle these power-hungry cards and a motherboard with 2 PCI-express x16 slots. Someone should verify this just to be sure as I'm taking this from other posts I've read.