The Alix is the LX800 (500mhz / 256 RAM) with 2x LAN + 2x mPCI.
The card is an Atheros AR5006XS - this card:
http://www.netgate.com/product_info.php?cPath=26_34&products_id=474
http://www.atheros.com/pt/AR5006XS.htm
It was the same price as the other units, and I thought Engenuis was pretty solid.
I have it set to 50% tx power, and have everything set to run through the right antenna, no diversity.
There are a couple of other APs, but they are about 1500-2000 feet away, and running on non-overlapping channels.