I'm trying to convert an Optiplex 990 (Desktop) into an entry-level gaming system. I plan to mostly run DCS (Digital Combat Simulator) and other high-detail flight sims which require high FPS and refresh rates. Since the DT is a low-profile housing I'm having trouble finding a performance GPU that will fit. Can anyone tell me what "specifically" I need to be searching for online? Even if the GPU requires more Watts than it has on-board (250W) I have an external 500W PSU on the way and don't mind leaving the side cover off. Anyone that can help please chime in as I've already ordered 2-Video Cards and neither of them fit...PLEASE HELP!!!!