I have successfully added a Netgear model MA311 WiFi PCI card to a WT9450XE and it works great!
Xpe recognized the card but had no drivers. I downloaded the latest XP driver for the MA311 from the Netgear site and put onto a USB drive and plugged the USB keychain-drive into the WT9450XE. Then I let XPe load the driver by pointing it to the USB drive when it detected the new hardware. It then came up running like a champ.