I don't know if the server will support a sound card but you can try. Looking at the docs here slot 1 and 2 are provided and controlled by the system board, slot 3 and 4 by cpu1 and 5, 6 by cpu2. So slot 1 is usable.
Got a T430 with RAID and Network NIC taking up PCIe Slots only have Slot 1 that is "Platform Controller Hub". Can I use Slot 1?
Dell PowerEdge T430 using PCIe Slot 1 for a Sound Blaster PCIe Card