Adding Video Card to HP DL580 G5 Server

The HP DL580 G5 Server comes with an integrated ATI ES1000 with 32MB embedded video SDRAM. This is inadequate for my needs. I need to increase the SDRAM to 512MB minimun.

The server has PCI-e x8 and x4 slots, and I have tried installing x16 and x1 Video cards in them but see no screen display. Could anyone please give me some ideas or recommend video cards that would work on the server?

Thanks.