Thanks for all the help and comments. I have started using the ip_conntrack_amanda module in my iptables setup and that seems to work fine.
The issue of stock packages vs. personalized compiles is an interesting philosophical debate I'd rather not get into at this point. Both approaches have their merits, and both are appropriate under certain circumstances. I prefer to use stock packages where they provide enough power and flexibility to solve the problem at hand. The combination of amanda, iptables, and ip_conntrack_amanda does that for me in this case. I understand that YMMV. Thanks again to all.
