Stuart,
Two things. The kernel can be updated on the server , and I would like to do that, please notify me when a good time will be to do the upgrade. There will be about 30 to 40 mins of downtime max . This will improve ram and cpu usage, as well as has some tweaks in the kernel for steam games.
Cpu(s): 1.1%us, 0.0%sy, 0.0%ni, 98.8%id, 0.0%wa, 0.0%hi, 0.1%si, 0.0%st
Mem: 4037988k total, 3995664k used, 42324k free, 224816k buffers
Swap: 4088532k total, 156k used, 4088376k free, 2389208k cached
As you can see your server is performing pretty optimal already. I will suggest to change your rate settings to the following:
sv_minrate 1000
sv_maxrate 50000
The settings prior were too close together and not broad enough for a large number of clients. The server was forcing itself to try and accomodate only a few clients rather than all. Please fix these settings and restart your server.
Also notify me as to when I can update the kernel on your server.
Thanks