Don't bother with calling Dell support regarding add on video cards with all but the very latest PE servers as it is an unsupported configuration.
Your best bet is to search these forum for previous PE 2950 video posts. Some posters have had limited success using some cards but in general, it's been a hit and miss affair on these older servers.
It is possible if the bios allowed you to disable the integrated graphics, as is the case on the T610 for example, but unfortunately with your server disabling the integrated graphics is not possible.