Erwin, you could experiment with (or implement) cpu_polling in your kernel to decrease the time it takes for the CPU to communicate with your network card(s) -which can be a bottleneck on busy sites. Fortunately FreeBSD has this option.
Add the following to your kernel and rebuild it, I've been using it with great success on my Dual Xeon system;
Code:
#Device polling
options DEVICE_POLLING
options HZ=1200