After having launched in March Airport 802.11n cards dedicated to the upgrade of Core Duo-based MacBook and iMac (US$149),
Quickertek has recently added a kit for upgrading a Mac mini to 802.11n (US$179); in addition to the tools and the upgrade card, it also includes an antenna. Such a price might prevent many users to perform the operation, as one can buy a Mac mini Core Duo from the Refurb Store for around 400€.
PS: we think Quickertek must read carefully our website, and offers the upgrade kit as soon as we release the procedure to perform the operation...