Airport Extreme 802.11n upgrade options for early Intel Core Duo iMac

Question

I have an iMac from mid 2006. I recently purchased a Timecapsule - partly for the wireless back ups, and partly to upgrade my wireless network to 802.11n. There is a software upgrade from Apple that upgrades older 802.11 a/b/g Airport cards in the iMac to 'n' standard. Here is the link:
http://store.apple.com/uk/product/D4141ZM/A?fnode=MTY1NDA0Mg&mco=MjIzMDkzNA
The page states that the upgrade is compatible "If you have a Mac with an Intel Core 2 Duo processor (except the 17-inch, 1.83GHz iMac)". What it doesn't tell you is that if you have an early version of the iMac (pre-Sept 2006) that shipped with the Intel Core Duo Processor (note - not the Core 2 Duo) then the upgrade will not work. I have also tried to install Airport Extreme updates (2007002 and 2008004) and these report that the hardware is not compatible. Doing some searching around these forums and others, the issue with the original Core Duo iMacs not being upgradeable to 802.11n is out there - shame Apple weren't more explicit.
I have seen that there are various USB based 802.11n adapters available. Whilst searching on this topic, I also came across a site offering various Mac upgrades, including an upgrade to the Airport card to upgrade wireless capability from 802.11g to 802.11n. It looks like a straight replacement for the internal card - link here:
http://www.macupgrades.co.uk/store/productinfo.php?productsid=461
The company offering this is in the UK, but the product appears to be from a Sonnet, a US company. Does anyone out there have experience of installing this product (or having it installed) and can you comment on how it performs? Is it a seamless replacement for the original Airport card?

Answer 1

What it doesn't tell you is that if you have an early version of the iMac (pre-Sept 2006) that shipped with the Intel Core Duo Processor (note - not the Core 2 Duo) then the upgrade will not work.
If it says you need to have a Core "2" Duo processor, then it seems to me they are telling you very clearly that it will not work with the earlier Core (no "2") Duo iMacs.
The "late 2006" iMacs with Core 2 Duo (except for that one education model they mentioned) have wireless networking hardware that is 802.11n capable. When they were initially sold, Apple chose to NOT enable the "n" capability for some reason; maybe because the standard was still in flux and not enough testing had been done with the driver. Later, they enabled the "n" capability with a firmware update. But that was only possible because the wireless hardware was already capable of doing "n."
Earlier iMacs do not have this hardware so there is no way to enable it with a firmware or software update. 802.11g is plenty fast enough for Internet access (you won't notice a difference with "n"). If you are using Time Machine over wireless, it may take a while longer to do that initial backup (you could connected it by Ethernet cable when it is doing that initial backup), but subsequent backups are incremental, so the "g" versus "n" speed difference will not be as critical. Since your iMac is Core Duo (32-bit) and the future of Mac OS X is 64-bit, especially after Snow Leopard's release, it may be best to save your money and keep your iMac intact (not opened).