Dual-band 802.11n support, in AP mode?

[Chuck Burns]

Subject pretty much says it all.

I am in the market for a supported dual-band 802.11n wifi adapter, that 
can be used with FreeBSD to run as an access point.

I have an old athlonxp 2000 that I intend to make into a custom router, 
but need to find a PCI (not PCI-e) or USB2.x adapter that I can use to 
provide wireless service to my home.

I have 2 gigabit cards in the box already, as well as an external 5port 
gigabit switch..

I also have a single-band 2.4ghz .11n router currently, that I am using 
as an AP-only, but I would like to support the 5ghz band.

I am open to the idea of simply replacing the router with a dual-band 
AP.. but I would prefer a PCI adapter.

Any ideas on supported chipsets/adapters that meet these requirements?

Thanks,
Chuck Burns <break19 at gmail.com>