Audigy Sound Card uses PCI express x1 (single data lane).  It should work on any of the black/blue PCIe slots except the white PCI slot.  If it is working fine right now, keep it in the bottom slot.  That is a PCIe x16 wired as x4 slot.
Hello Friends I'm installing an Audigy Sound Blaster Sound Card in my 3620. I have a blue PCi slot and a black PCi slot (on the bottom). Its currently in the bottom Black slot and working fine ... Which slot should I have installed it in? Thank You
Installing Sound Card into 3620 Precision Desktop