I have a Dell XPS 8900 Special Edition, Windows 10 Pro, i7 6700k 6th Gen Quad core, 16GB of Ram, a NVIDIA GeForce GTX 745 4GB Memory. I would like to upgrade the Graphics card, but to what ?  What will work, ( I would want the best that will work, with out having to put in a new Power supply).

  I would like to stay with NVIDIA GeForce.                          Thanks  Jim