Going back to the original question, why not use something like this:
http://www.amfeltec.com/products/flexible-minipcie-to-minipci-adapter.php
It converts mini pci-e to mini pci, allowing the use of well know soekris vpn 1411 cards, etc.On faster systems, you'd easily saturate the bus on those and probably get poorer performance with the card in than without the card.
Hopefully once we get FreeBSD 9 builds going we'll get AESNI included and see how that helps :-)
AESNI needs a lot more work before it's going to help. ;-)
Work proceeds.