NAI has given up on the idea that only they can sell an "approved" NIC. I have the email from them about this. As long as you purchase the correct brand/model of NIC, it's "approved" I have the CBE2 Xircom which I bought from buy.com and saved quite a bit over the list price charged by NAI and it works fine.
A side bar is for quick and dirty sniffing, ANY nic will work as long as it's "promiscious". You give up things like runts and fragments but for monitoring normal traffic, it's a cheap way to go.
Mike [sig][/sig]