Yes your rig can run the card, and 4GB is absolutely plenty for FHD display, you'd need tri 1440p if you want to utilize 6 or 8GB of VRAM, even in SLI. GTX 980 is a great card, 170W TDP will run with ease if your 560 Ti runs well. I don't really know any better single GPU card. Feel free to upgrade, and I'd also upgrade PSU when you plan to SLI, as Thermaltake can not be trusted for high loads.