That should be fine. All you need is a PCIE x1 slot, which you have, and the drivers which are available here. The SB card has instructions and it is an extremely easy install, and the install guide is also on the same page as the drivers.
I am having sound issues with my XPS 8940. I get a lot of popping when playing media. I have isolated the issue to the PC and have decided unless there is a fix for this, to add a PCIe sound card to the system. I can not find any information or guides on how to properly add a PCIe sound card to this system. So I need some help here. I am looking at a Creative Sound Blaster Audigy PCIe RX 7.1 card as my replacement.    
XPS 8940, adding a PCIe sound card