Sonnet Technologies has released the US$99.95 Aria Extreme N PCI
802.11n wireless PCI card
(http://www.sonnettech.com/product/ariaextremenpci.html), which
delivers draft 802.11n wireless network connectivity to Power Mac G5,
Power Mac G4, and Windows desktop computers with an available PCI or
PCI-X slot. It's backward compatible with 802.11b and 802.11g routers
and other equipment.
Draft 802.11n networking offers enhanced performance compared to
802.11g, the previous wireless network standard. When used in 802.11n
networks, Aria Extreme N PCI can purportedly achieve up to 2.5 times
the speed and twice the range than when used in an 802.11g network.
Sonnet's Aria Extreme N PCI features three antennas (2TX/3RX) to
maximize its performance with 802.11n routers that also feature
multiple radios and antennas.

802.11n devices utilize MIMO (multiple input, multiple output)
technology that enables multiple concurrent data stream transmission,
and provides enough bandwidth to allow simultaneous high-speed
Internet access, HD video streaming, large file transferring, VoIP
telephony, and more. Aria Extreme N PCI supports WEP, WPA and WPA2
security protocols along with AES and TKIP encryption for secure
network configuration.

The Aria Extreme N PCI works with all AirPort Extreme and AirPort
Express base stations and equivalent wireless hubs. It's compatible
with Mac OS X 10.4 and higher. Mac OS 10.4 and later