I have an opportunity to buy a used Dell T5400 for a very reasonable price.
CPU: Xeon E5420 Clock: 2500 Mhz Cores: 4 - Quad Core RAM: 4GB DDR3 Disk: 250GB GPU: nVidia Quadro NVS DMS->2x DVI OS: Windows 8.1 Professional
Obviously this is a work computer. The gfx card is really not fit for gaming (I have the very same model at work, just with 20GB of RAM, tried running some games and the framerate is abysmal). Most likely I'd purchase more RAM, and moving disks from the old computer I'd have some 1.5TB of storage. But the primary decision for now is the gfx card.
My budget for the gfx card is around $250-$300. The primary use would be games, with some graphics editing, programming and home use on the side.
Which gfx card that fits that model, that would fit within the budget would provide optimal gaming performance?