It will work (or should
) with no problems. All the machines I've got here have both wireless and wired cards in them.
As a slight aside - hope you are not paying too much for the Netgear. There are a lot of the Linksys wma11b's going on Ebay at the moment (due to the recent PCWorld sale). You shouldn't pay more than about £20 plus postage for one of those.
(Yes it's only 11b instead of 11g/b though - but shouldn't have a problem with streaming music).
Also, since it's wireless, you shouldn't need to worry about putting another card in
BTW the XBox, running the correct software, works very well as a music server for networks.