Choosing quality server components for your system makes a big difference in terms of reliability and performance of a system.
Here's an example graph showing traffic on a Sippy Media Gateway. On the left side, it shows the Packet Per Seconds, CPU usage and Bandwidth usage when running a Broadcom Network card. The day after we installed a server grade Intel Network card. As one can see, at the equivalent PPS and bandwidth levels, this system had a 15% CPU reduction, and overall, the system was able to handle significantly more network traffic.