aCard + Tri-Band for Mac Mini
802.11 a/b/g/n for Intel Mac Minis
*will not work for PowerPC Mac Minis, please check before ordering.

Not even Apple offers this.
This is the best wireless conceivable for Mac Minis. This goes beyond an 802.11 n upgrade. This new product allows for full wireless speed. The QuickerTek aCard provides 802.11 a, 802.11 b, 802.11 g,
and 802.11 n wireless compatibility. What that means is the computer can network using 802.11 a and the 5 gigahertz band. What this means for you: a cleaner signal with far less dropout. The 2.4 ghz band is crowded with other devices (including WiFi networks, cell phones, and microwave ovens).

Apple's new Base Station Extreme supports a/b/g/n but Apple won't upgrade your Mac to 802.11 a/b/g/n. Apple only offers 802.11 b/g/n in its Macs. This means they DO NOT support the 5 gigahertz band. The 5 ghz band is optional for 802.11 n, not mandatory.

This makes great use of MIMO technology. The 802.11 a/b/g/n devices aimed at high performance will include MIMO is Multi-Input Multi-Output, meaning both the Base Station (or Router) and the Mac (or PC) must have multiple antennas to employ something called “spatial-multiplexing”. This is most important in the speed department, think of it as having a 4 lane highway instead of a 2 lane highway, and having plenty of traffic for the former!

works with all the wireless standards*:
802.11 a - 5.0 ghz, 300 Mbits per second
802.11 b - 2.4 ghz, 11 Mbits per second
802.11 g - 2.4 ghz, 54 Mbits per second
802.11 n - 2.4 ghz, 300 Mbits per second

*actual speed dependent on AirPort Base Station (or Router) settings and physical barriers.