I haven't tried it, but a Broadcom Crystal HD decoder card should work in the 9's Wifi slot. As stated above, you'll be giving up onboard Wifi.
The 9 has a full-height Wifi slot, and the Crystal card has full (older) and half-height versions, so make sure you have a bracket if needed (or other means to secure the card).
...or you can do the obvious upgrade to the Wifi slot, and opt for a better Wifi card. I chose the Intel 5100 for my 9. In the full-height version, it seemed like the best card (ABGN, 2.4GHz and 5GHz) that was an easy upgrade. No half-height bracket needed, no additional antennas needed.